Found 46 papers in cond-mat
Date of feed: Wed, 28 Jun 2023 00:30:00 GMT

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Coulomb screening and scattering in atomically thin transistors across dimensional crossover. (arXiv:2306.14925v1 [cond-mat.mes-hall])
Shihao Ju, Binxi Liang, Jian Zhou, Danfeng Pan, Yi Shi, Songlin Li

Layered two-dimensional dichalcogenides are potential candidates for post-silicon electronics. Here, we report insightfully experimental and theoretical studies on the fundamental Coulomb screening and scattering effects in these correlated systems, in response to the changes of three crucial Coulomb factors, including electric permittivity, interaction length, and density of Coulomb impurities. We systematically collect and analyze the trends of electron mobility with respect to the above factors, realized by synergic modulations on channel thicknesses and gating modes in dual-gated MoS2 transistors with asymmetric dielectric cleanliness. Strict configurative form factors are developed to capture the subtle parametric changes across dimensional crossover. A full diagram of the carrier scattering mechanisms, in particular on the pronounced Coulomb scattering, is unfolded. Moreover, we clarify the presence of up to 40% discrepancy in mobility by considering the permittivity modification across dimensional crossover. The understanding is useful for exploiting atomically thin body transistors for advanced electronics.


Toward a new theory of the fractional quantum Hall effect: The many-body spectra and energy gaps at $\nu<1$. (arXiv:2306.14931v1 [cond-mat.mes-hall])
S. A. Mikhailov

In a recent paper (arXiv:2206.05152v4), using the exact diagonalization technique, I calculated the energy and other physical properties (electron density, pair correlation function) of a system of $N\le 7$ two-dimensional electrons at the Landau level filling factor $\nu=1/3$, and showed that the variational many-body wave function proposed for this filling factor by Laughlin is far from the true ground state. In this paper I continue to study exact properties of a small ($N\le 7$) system of two-dimensional electrons lying on the lowest Landau level. I analyze the energies and electron densities of the systems with $N\le 7$ electrons continuously as a function of the magnetic field in the range $1/4\lesssim\nu<1$. The physical mechanisms of the appearance of energy gaps in many-particle electron spectra are elucidated. The results obtained clarify the true nature of the ground and excited states of the considered systems.


Metal-insulator transition in transition metal dichalcogenide heterobilayer: accurate treatment of interaction. (arXiv:2306.14954v1 [cond-mat.str-el])
Yubo Yang, Miguel Morales, Shiwei Zhang

Transition metal dichalcogenide superlattices provide an exciting new platform for exploring and understanding a variety of phases of matter. The moir\'e continuum Hamiltonian, of two-dimensional jellium in a modulating potential, provides a fundamental model for such systems. Accurate computations with this model are essential for interpreting experimental observations and making predictions for future explorations. In this work, we combine two complementary quantum Monte Carlo (QMC) methods, phaseless auxiliary field quantum Monte Carlo and fixed-phase diffusion Monte Carlo, to study the ground state of this Hamiltonian. We observe a metal-insulator transition between a paramagnetic and a $120^\circ$ N\'eel ordered state as the moir\'e potential depth and the interaction strength are varied. We find significant differences from existing results by Hartree-Fock and exact diagonalization studies. In addition, we benchmark density-functional theory, and suggest an optimal hybrid functional which best approximates our QMC results.


Self-bound Vortex Lattice in a Rapidly Rotating Quantum Droplet. (arXiv:2306.14958v1 [cond-mat.quant-gas])
Qi Gu, Xiaoling Cui

A rapidly rotating Bose gas in the quantum Hall limit is usually associated with a melted vortex lattice. In this work, we report a self-bound and visible triangular vortex lattice without melting for a two-dimensional Bose-Bose droplet rotating in the quantum Hall limit, i.e., with rotation frequency $\Omega$ approaching the trapping frequency $\omega$. Increasing $\Omega$ with respect to interaction strength $U$, we find a smooth crossover of vortex lattice droplet from a needling regime, as featured by small vortex cores and an equilibrium flat-top surface, to the lowest-Landau-level regime with Gaussian-extended cores spreading over the whole surface. The surface density of such rotating droplet is higher than that of a static one, and their ratio is found to be a universal function of $\Omega/U$. We have demonstrated these results by both numerical and variational methods. The results pave the way for future experimental exploration of rapidly rotating ultracold droplets into the quantum Hall limit.


Topological phase transition revealed by electron waiting times. (arXiv:2306.14964v1 [cond-mat.supr-con])
Paramita Dutta, Jorge Cayao, Annica M. Black-Schaffer, Pablo Burset

The analysis of waiting times of electron transfers has recently become experimentally accessible owing to advances in noninvasive probes working in the short-time regime. We study electron waiting times in a topological Andreev interferometer: a superconducting loop with controllable phase difference connected to a quantum spin Hall edge. The edge state helicity enables the transfer of electrons and holes into separate leads, with transmission controlled by the loop's phase difference $\phi$. In this setup, a topological phase transition with emerging Majorana bound states occurs at $\phi=\pi$. The waiting times for electron transfers across the junction are sensitive to the phase transition, but are uncorrelated for all $\phi$. By contrast, in the topological phase, the waiting times of Andreev-scattered holes show a strong correlation and the crossed (hole-electron) distributions feature a unique behavior. Both effects exclusively result from the presence of Majorana bound states. Consequently, electron waiting times could circumvent some of the challenges for detecting topological superconductivity and Majorana states beyond conductance signatures.


Quantum interference of pseudospin-1 fermions. (arXiv:2306.14967v1 [cond-mat.mes-hall])
Adesh Singh, G. Sharma

Quantum interference is studied in a three-band model of pseudospin-one fermions in the $\alpha-\mathcal{T}_3$ lattice. We derive a general formula for magnetoconductivity that predicts a rich crossover between weak localization (WL) and weak antilocalization (WAL) in various scenarios. Recovering the known results for graphene ($\alpha=0$), we remarkably discover that WAL is notably enhanced when one deviates slightly from the graphene lattice, i.e. when $\alpha>0$, even though Berry's phase is no longer $\pi$. This is attributed to the presence of multiple Cooperon channels. Upon further increasing $\alpha$, a crossover to WL occurs that is maximal for the case of the Dice lattice ($\alpha=1$). Our work distinctly underscores the role of non-trivial band topology in the localization properties of electrons confined to the two-dimensional $\alpha-\mathcal{T}_3$ lattice.


The Underlying Scaling Laws and Universal Statistical Structure of Complex Datasets. (arXiv:2306.14975v1 [cs.LG])
Noam Levi, Yaron Oz

We study universal traits which emerge both in real-world complex datasets, as well as in artificially generated ones. Our approach is to analogize data to a physical system and employ tools from statistical physics and Random Matrix Theory (RMT) to reveal their underlying structure. We focus on the feature-feature covariance matrix, analyzing both its local and global eigenvalue statistics. Our main observations are: (i) The power-law scalings that the bulk of its eigenvalues exhibit are vastly different for uncorrelated random data compared to real-world data, (ii) this scaling behavior can be completely recovered by introducing long range correlations in a simple way to the synthetic data, (iii) both generated and real-world datasets lie in the same universality class from the RMT perspective, as chaotic rather than integrable systems, (iv) the expected RMT statistical behavior already manifests for empirical covariance matrices at dataset sizes significantly smaller than those conventionally used for real-world training, and can be related to the number of samples required to approximate the population power-law scaling behavior, (v) the Shannon entropy is correlated with local RMT structure and eigenvalues scaling, and substantially smaller in strongly correlated datasets compared to uncorrelated synthetic data, and requires fewer samples to reach the distribution entropy. These findings can have numerous implications to the characterization of the complexity of data sets, including differentiating synthetically generated from natural data, quantifying noise, developing better data pruning methods and classifying effective learning models utilizing these scaling laws.


Heat Conductance of the Quantum Hall Bulk. (arXiv:2306.14977v1 [cond-mat.mes-hall])
Ron Aharon Melcer, Avigail Gil, Vladimir Umansky, Moty Heiblum, Yuval Oreg, Ady Stern, Erez Berg

The Quantum Hall Effect (QHE) is the prototypical realization of a topological state of matter. It emerges from a subtle interplay between topology, interactions, and disorder. The disorder enables the formation of localized states in the bulk that stabilize the quantum Hall states with respect to the magnetic field and carrier density. Still, the details of the localized states and their contribution to transport remain beyond the reach of most experimental techniques. Here, we describe an extensive study of the bulk's heat conductance. Using a novel 'multi-terminal' device, we separate the longitudinal thermal conductance (due to bulk's contribution) $\kappa_{xx}T$ from the two-terminal value $\kappa_{2T}T$, by eliminating the contribution of the edge modes. We find that when the field is tuned away from the conductance plateau center, the electronic states of the bulk conduct heat efficiently while the bulk remains electrically insulating. For fragile fractional states, such as the non-Abelian $\nu=5/2$, we observe a finite $\kappa_{xx}T$ throughout the plateau. We identify the localized states as the cause of the finite $\kappa_{xx}T$ and propose a theoretical model which qualitatively explains our findings.


Topological triple phase transition in non-Hermitian quasicrystals with complex asymmetric hopping. (arXiv:2306.14987v1 [cond-mat.dis-nn])
Shaina Gandhi, Jayendra N. Bandyopadhyay

The triple phase transitions or simultaneous transitions of three different phases, namely topological, parity-time (PT) symmetry breaking, and metal-insulator transitions, are observed in an extension of PT symmetric non-Hermitian Aubry-Andr\'e-Harper model. In this model, besides non-Hermitian complex quasi-periodic onsite potential, non-Hermiticity is also included in the nearest-neighbor hopping terms. Moreover, the nearest-neighbor hopping terms is also quasi-periodic. The presence of two non-Hermitian parameters, one from the onsite potential and another one from the hopping part, ensures PT symmetry transition in the system. In addition, tuning these two non-Hermitian parameters, we identify a parameters regime, where we observe the triple phase transition. Following some recent studies, an electrical circuit based experimental realization of this model is also discussed.


Trace Element Partitioning between CAI-Type Melts and Grossite, Melilite, Hibonite, and Olivine. (arXiv:2306.15001v1 [astro-ph.EP])
Gokce Ustunisik, Denton S. Ebel, David Walker, Roger L. Nielsen, Marina E. Gemma

We determined the mineral-melt partition coefficients (Di's) and the compositional and/or temperature dependency between grossite, melilite, hibonite, olivine and Ca-, Al-inclusion (CAI)-type liquids for a number of light (LE), high field strength (HFSE), large ion lithophile (LILE), and rare earth (REE) elements including Li, Be, B, Sr, Zr, Nb, Ba, La, Ce, Eu, Dy, Ho, Yb, Hf, Ta, Th. A series of isothermal crystallization experiments was conducted at 5 kbar pressure and IW+1 in graphite capsules. The starting compositions were selected based on the calculated and experimentally confirmed phase relations during condensation in CI dust-enriched systems (Ebel and Grossman, 2000; Ebel, 2006; Ustunisik et al., 2014). Partition coefficients between melt and gehlenite, hibonite, and grossite show that the trace element budget of igneous CAIs is controlled by these three major Al-bearing phases in addition to pyroxene. In general, LE, LILE, REE, and HFSE partition coefficients (by mass) decrease in the order of Di(Gehlenite-Melt) > Di(Hibonite-Melt) > Di(Grossite-Melt). Results suggest that Di(Gehlenite-Melt) vary by a factor of 2-3 in different melt compositions at the same T (~1500 C). Increased melt Al and Ca, relative to earlier work, increases the compatibility of Di(Gehlenite-Melt), and also the compatibility of Di(Hibonite-Melt), especially for La and Ce. Olivine partitioning experiments confirm that olivine contribution to the trace element budget of CAIs is small due to the low Di(Olivine-Melt) at a range of temperatures while D-Eu, Yb(Olivine-Melt) are sensitive to changes in T and oxygen fugacity. The development of a predictive model for partitioning in CAI-type systems would require more experimental data and the use of analytical instruments capable of obtaining single phase analyses for crystals < 5 micron.


Quantifying the Topology of Magnetic Skyrmions in three Dimensions. (arXiv:2306.15003v1 [cond-mat.mtrl-sci])
David Raftrey, Simone Finizio, Rajesh V. Chopdekar, Scott Dhuey, Temuujin Bayaraa, Paul Ashby, Jörg Raabe, Tiffany Santos, Sinéad Griffin, Peter Fischer

Magnetic skyrmions have so far been treated as two-dimensional spin structures characterized by a topological winding number describing the rotation of spins across the skyrmion. However, in real systems with a finite thickness of the material being larger than the magnetic exchange length, the skyrmion spin texture extends into the third dimension and cannot be assumed as homogeneous. Using soft x-ray laminography we reconstruct with about 20nm spatial (voxel) resolution the full three-dimensional spin texture of a skyrmion in an 800 nm diameter and 95 nm thin disk patterned into a trilayer [Ir/Co/Pt] thin film structure. A quantitative analysis finds that the evolution of the radial profile of the topological skyrmion number and the chirality is non-uniform across the thickness of the disk. Estimates of local micromagnetic energy densities suggest that the changes in topological profile are related to non-uniform competing energetic interactions. Theoretical calculations and micromagnetic simulations are consistent with the experimental findings. Our results provide the foundation for nanoscale magnetic metrology for future tailored spintronics devices using topology as a design parameter, and have the potential to reverse-engineer a spin Hamiltonian from macroscopic data, tying theory more closely to experiment.


Particle-Based Simulations of Electrophoretic Deposition with Adaptive Physics Models. (arXiv:2306.15009v1 [cond-mat.mes-hall])
John J. Karnes, Andrew J. Pascall, Christoph Rehbock, Vaijayanthi Ramesh, Marcus A. Worsley, Stephan Barcikowski, Elaine Lee, Brian Giera

This work represents an extension of mesoscale particle-based modeling of electrophoretic deposition (EPD), which has relied exclusively on pairwise interparticle interactions described by Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. With this standard treatment, particles continuously move and interact via excluded volume and electrostatic pair potentials under the influence of external fields throughout the EPD process. The physics imposed by DLVO theory may not be appropriate to describe all systems, considering the vast material, operational, and application space available to EPD. As such, we present three modifications to standard particle-based models, each rooted in the ability to dynamically change interparticle interactions as simulated deposition progresses. This approach allows simulations to capture charge transfer and/or irreversible adsorption based on tunable parameters. We evaluate and compare simulated deposits formed under new physical assumptions, demonstrating the range of systems that these adaptive physics models may capture.


Asymmetry of social interactions and its role in link predictability: the case of coauthorship networks. (arXiv:2306.15022v1 [cs.SI])
Kamil P. Orzechowski, Maciej J. Mrowinski, Agata Fronczak, Piotr Fronczak

The paper provides important insights into understanding the factors that influence tie strength in social networks. Using local network measures that take into account asymmetry of social interactions we show that the observed tie strength is a kind of compromise, which depends on the relative strength of the tie as seen from its both ends. This statement is supported by the Granovetter-like, strongly positive weight-topology correlations, in the form of a power-law relationship between the asymmetric tie strength and asymmetric neighbourhood overlap, observed in three different real coauthorship networks and in a synthetic model of scientific collaboration. This observation is juxtaposed against the current misconception that coauthorship networks, being the proxy of scientific collaboration networks, contradict the Granovetter's strength of weak ties hypothesis, and the reasons for this misconception are explained. Finally, by testing various link similarity scores, it is shown that taking into account the asymmetry of social ties can remarkably increase the efficiency of link prediction methods. The perspective outlined also allows us to comment on the surprisingly high performance of the resource allocation index -- one of the most recognizable and effective local similarity scores -- which can be rationalized by the strong triadic closure property, assuming that the property takes into account the asymmetry of social ties.


Origin of Charge Density Wave in Topological Semimetals SrAl4 and EuAl4. (arXiv:2306.15068v1 [cond-mat.mtrl-sci])
Lin-Lin Wang, Niraj K. Nepal, Paul C. Canfield

Topological semimetals in BaAl4-type structure have shown many interesting behaviors, such as charge density wave (CDW) in SrAl4 and EuAl4, but not the isostructural and isovalent BaAl4, SrGa4 and BaGa4, although they all host Dirac points and nodal line Dirac-like dispersion. Here using Wannier functions based on density functional theory, we have calculated the susceptibility functions with millions of k-points to reach the small q-vector and study the origin and driving force behind the CDW. Our comparative study reveals that the origin of the CDW in SrAl4 and EuAl4 is the strong electron-phonon coupling interaction for the transverse acoustic mode at small q-vector along the {\Gamma}-Z direction besides the maximum of the real part of the susceptibility function from the nested Fermi surfaces of the Dirac-like bands, which explains well the absence of CDW in the other three closely related compounds in a good agreement with experiment.


Controlling the radiation dynamics of MoSe2/WSe2 interlayer excitons via in-situ tuning the electromagnetic environment. (arXiv:2306.15101v1 [cond-mat.mtrl-sci])
Bo Han, Chirag Palekar, Sven Stephan, Frederik Lohof, Alexander Steinhoff, Jens-Christian Drawer, Victor Mitryakhin, Lukas Lackner, Martin Silies, Barbara Rosa, Martin Esmann, Falk Eilenberger, Christopher Gies, Stephan Reitzenstein, Christian Schneider

We show that the spontaneous emission rate of the interlayer excitons in a twisted WSe2-MoSe2 heterobilayer can be precisely tailored in a low-temperature open optical microcavity via the Purcell effect. We engineer the local density of optical states in our resonator structures in two complementary experimental settings. In the first approach, we utilize an ultra-low quality factor planar vertical cavity structure, which develops multiple longitudinal modes that can be consecutively brought to resonance with the broad interlayer exciton spectrum of our heterostructure. Time-resolved photoluminescence measurements reveal that the interlayer exciton lifetime can thus be periodically tuned with an amplitude of around 100 ps. The resulting oscillations of the exciton lifetime allows us to extract a free-space radiative exciton lifetime of 2.2 ns and an approximately 15 % quantum efficiency of the interlayer excitons. We subsequently engineered the local density of optical states by introducing a spatially confined and fully spectrally tunable Tamm-plasmon resonance. The dramatic redistribution of the local optical modes in this setting allows us to encounter a profound inhibition of spontaneous emission of the interlayer excitons by a factor of 3.3. Our results will further boost the cavity-mediated collective emission phenomena such as super-radiance. We expect that specifically engineering the inhibition of radiation from moire excitons is a powerful tool to steer their thermalization, and eventually their condensation into coherent condensate phases.


Non-invasive digital etching of van der Waals semiconductors. (arXiv:2306.15139v1 [cond-mat.mtrl-sci])
Jian Zhou, Chunchen Zhang, Li Shi, Xiaoqing Chen Tae-Soo Kim, Minseung Gyeon, Jian Chen Jinlan Wang, Linwei Yu Xinran Wang Kibum Kang, Emanuele Orgiu, Paolo Samorì, Kenji Watanabe, Takashi Taniguchi, Kazuhito Tsukagoshi, Peng Wang, Yi Shi, Songlin Li

The capability to finely tailor material thickness with simultaneous atomic precision and non-invasivity would be useful for constructing quantum platforms and post-Moore microelectronics. However, it remains challenging to attain synchronized controls over tailoring selectivity and precision. Here we report a protocol that allows for non-invasive and atomically digital etching of van der Waals transition-metal dichalcogenides through selective alloying via low-temperature thermal diffusion and subsequent wet etching. The mechanism of selective alloying between sacrifice metal atoms and defective or pristine dichalcogenides is analyzed with high-resolution scanning transmission electron microscopy. Also, the non-invasive nature and atomic level precision of our etching technique are corroborated by consistent spectral, crystallographic and electrical characterization measurements. The low-temperature charge mobility of as-etched MoS$_2$ reaches up to $1200\,$cm$^{2}\cdot$V$^{-1}\cdot$s$^{-1}$, comparable to that of exfoliated pristine counterparts. The entire protocol represents a highly precise and non-invasive tailoring route for material manipulation.


Electrocatalytic Performance of 2D Monolayer WSeTe Janus Transition Metal Dichalcogenide for Highly Efficient H2 Evolution Reaction. (arXiv:2306.15249v1 [cond-mat.mtrl-sci])
Vikash Kumar, Shrish Nath Upadhyay, Dikeshwar Halba, Srimanta Pakhira

Now-a-days, the development of clean and green energy sources is the prior interest of research due to increasing global energy demand and extensive usage of fossil fuels that create pollutants. Hydrogen has the highest energy density by weight among all chemical fuels. For the commercial-scale production of hydrogen, water electrolysis is the best method which in turn requires an efficient, cost-effective and earth-abundant electrocatalyst. Recent studies have shown that the 2D Janus TMDs are highly effective in the electrocatalytic activity for HER. Herein we report a 2D monolayer WSeTe Janus TMD electrocatalyst for HER. We studied the electronic properties of 2D monolayer WSeTe Janus TMD using periodic DFT calculations, and the direct electronic band gap was obtained to be 2.39 eV. After the calculations of electronic properties, we explored the HER intermediates including various transition state structures (Volmer TS, Heyrovsky TS, and Tafel TS) using a molecular cluster model of WSeTe noted as W10Se9Te12. The present calculations revealed that the 2D monolayer WSeTe Janus TMD is a potential electrocatalyst for HER. It has the lowest energy barriers for all the TSs among other TMDs, such as MoS2, Mn-MoS2, MoSSe, etc. The calculated Heyrovsky energy barrier (= 8.72 kcal.mol-1) for the Volmer-Heyrovsky mechanism is larger than the Tafel energy barrier (=3.27 kcal.mol-1) in the Volmer-Tafel mechanism. Hence our present study suggests that the formation of H2 is energetically more favorable via the Vomer-Tafel mechanism. This work helps shed light on the rational design of effective HER catalysts.


Platinum-absorbed Defective 2D Monolayer Boron Nitride: A Promising Electrocatalyst for O2 Reduction Reaction. (arXiv:2306.15252v1 [cond-mat.mtrl-sci])
Lokesh Yadav, Srimanta Pakhira

The large bandgap and strong covalent bonds of hexagonal boron nitride (hBN) had long been thought to be chemically inert. Due to its inertness with saturated robust covalent bonds, the pristine 2D monolayer hBN cannot be functionalized for applications of energy conversion. Therefore, it is necessary to make the 2D hBN chemically reactive for potential applications. Here, we have computationally designed a single nitrogen (N) and boron (B) di-vacancy of the 2D monolayer hBN, noted by VBN defective-BN (d-BN), to activate the chemical reactivity, which is an effective strategy to use the d-BN for potential applications. Single Pt atom absorbed on the defective area of the VBN d-BN acts as a single-atom catalyst which exhibits distinctive performances for O2 reduction reaction (ORR). First-principles based dispersion-corrected periodic hybrid Density Functional Theory (DFT-D) method has been employed to investigate the equilibrium structure and properties of the Pt-absorbed 2D defective boron nitride (Pt-d-BN). The present study shows the semiconducting character of Pt-d-BN with an electronic bandgap of 1.30 eV, which is an essential aspect of the ORR. The ORR mechanism on the surface of 2D monolayer Pt-d-BN follows a 4e-reduction route because of the low barriers to OOH formation and dissociation, H2O2 instability and water production at the Pt-d-BN surface. Here, both the dissociative and associative ORR mechanisms have been investigated, and it is found that results for both mechanisms with the ORR pathways are almost equally favorable. Therefore, it can be mentioned here that the 2D monolayer Pt-d-BN exhibits a high selectivity for the four-electron reduction pathway. According to the calculations of the relative adsorption energy of each step in ORR, the Pt-d-BN is anticipated to exhibit substantial catalytic activity.


Closest Wannier functions to a given set of localized orbitals. (arXiv:2306.15296v1 [cond-mat.mtrl-sci])
Taisuke Ozaki

A non-iterative method is presented to calculate the closest Wannier functions (CWFs) to a given set of localized guiding functions, such as atomic orbitals, hybrid atomic orbitals, and molecular orbitals, based on minimization of a distance measure function. It is shown that the minimization is directly achieved by a polar decomposition of a projection matrix via singular value decomposition, making iterative calculations and complications arising from the choice of the gauge irrelevant. The disentanglement of bands is inherently addressed by introducing a smoothly varying window function and a greater number of Bloch functions, even for isolated bands. In addition to atomic and hybrid atomic orbitals, we introduce embedded molecular orbitals in molecules and bulks as the guiding functions, and demonstrate that the Wannier interpolated bands accurately reproduce the targeted conventional bands of a wide variety of systems including Si, Cu, the TTF-TCNQ molecular crystal, and a topological insulator of Bi$_2$Se$_3$. We further show the usefulness of the proposed method in calculating effective atomic charges. These numerical results not only establish our proposed method as an efficient alternative for calculating WFs, but also suggest that the concept of CWFs can serve as a foundation for developing novel methods to analyze electronic structures and calculate physical properties.


Water-methanol mixture confined in a graphene slit-pore. (arXiv:2306.15330v1 [cond-mat.soft])
Roger Bellido-Peralta, Fabio Leoni, Carles Calero, Giancarlo Franzese

Efficient and sustainable techniques for separating water-methanol mixtures are in high demand in the industry. Recent studies have revealed that membranes and 2D materials could achieve such separation. In our research, we explore the impact of a nanoconfining graphene slit-pore on the dynamics and structure of water-methanol mixtures. By Molecular Dynamics simulations of a coarse-grained model for water mixtures containing up to 25% methanol, we show that, for appropriate pore sizes, water tends to occupy the center of the pore. In contrast, methanol's apolar moiety accumulates near the hydrophobic walls. Additionally, modifying the pore's width leads to a non-monotonic change in the diffusivity of each component. However, water always diffuses faster than methanol, implying that it should be possible to identify an optimal configuration for water-methanol separation based on physical mechanisms. Our calculations indicate that one of the more effective pore sizes, 12.5{\AA}, is also mechanically stable, minimizing the energy cost of a possible filtering membrane.


Phase transitions associated with magnetic-field induced topological orbital momenta in a non-collinear antiferromagnet. (arXiv:2306.15332v1 [cond-mat.mtrl-sci])
Sihao Deng, Olena Gomonay, Jie Chen, Gerda Fischer, Lunhua He, Cong Wang, Qingzhen Huang, Feiran Shen, Zhijian Tan, Rui Zhou, Ze Hu, Libor Šmejkal, Jairo Sinova, Wolfgang Wernsdorfer, Christoph Sürgers

Resistivity measurements are widely exploited to uncover electronic excitations and phase transitions in metallic solids. While single crystals are preferably studied to explore crystalline anisotropies, these usually cancel out in polycrystalline materials. Here we show that in polycrystalline Mn3Zn0.5Ge0.5N with non-collinear antiferromagnetic order, changes in the diagonal and, rather unexpected, off-diagonal components of the resistivity tensor occur at low temperatures indicating subtle transitions between magnetic phases of different symmetry. This is supported by neutron scattering and explained within a phenomenological model which suggests that the phase transitions in magnetic field are associated with field induced topological orbital momenta. The fact that we observe transitions between spin phases in a polycrystal, where effects of crystalline anisotropy are cancelled suggests that they are only controlled by exchange interactions. The observation of an off-diagonal resistivity extends the possibilities for realising antiferromagnetic spintronics with polycrystalline materials.


Operability timescale of defect-engineered graphene. (arXiv:2306.15345v1 [cond-mat.mtrl-sci])
Nicola Melchioni, Luca Bellucci, Alessandro Tredicucci, Federica Bianco

Defects in the lattice are of primal importance to tune graphene chemical, thermal and electronic properties. Electron-beam irradiation is an easy method to induce defects in graphene following pre-designed patterns, but no systematic study of the time evolution of the resulting defects is available. In this paper, the change over time of defected sites created in graphene with low-energy ($\leq 20$ keV) electron irradiation is studied both experimentally via micro-Raman spectroscopy for a period of $6\times 10^3$ hours and through molecular dynamics simulations. During the first 10 h, the structural defects are stable at the highest density value. Subsequently, the crystal partially reconstructs, eventually reaching a stable, less defected condition after more than one month. The simulations allow the rationalization of the processes at the atomic level and confirm that the irradiation induces composite clusters of defects of different nature rather than well-defined nanoholes as in the case of high-energy electrons. The presented results identify the timescale of the defects stability, thus establishing the operability timespan of engineerable defect-rich graphene devices with applications in nanoelectronics. Moreover, long-lasting chemical reactivity of the defective graphene is pointed out. This property can be exploited to functionalize graphene for sensing and energy storage applications.


Domain wall dynamics in classical spin chains: free propagation, subdiffusive spreading, and topological soliton emission. (arXiv:2306.15351v1 [cond-mat.stat-mech])
Adam J. McRoberts, Thomas Bilitewski, Masudul Haque, Roderich Moessner

The non-equilibrium dynamics of domain wall initial states in a classical anisotropic Heisenberg chain exhibits a striking coexistence of apparently linear and non-linear behaviours: the propagation and spreading of the domain wall can be captured quantitatively by \textit{linear}, i.e. non-interacting, spin wave theory absent its usual justifications; while, simultaneously, for a wide range of easy-plane anisotropies, emission can take place of stable topological solitons -- a process and objects intrinsically associated with interactions and non-linearities. The easy-axis domain wall only has transient dynamics, the isotropic one broadens diffusively, while the easy-plane one yields a pair of ballistically counter-propagating domain walls which, unusually, broaden \textit{subdiffusively}, their width scaling as $t^{1/3}$.


Gas dependent hysteresis in MoS$_2$ field effect transistors. (arXiv:2306.15353v1 [cond-mat.mes-hall])
F. Urban, F. Giubileo, A. Grillo, L. Iemmo, G. Luongo, M. Passacantando, T. Foller, L. Madauß, E. Pollmann, M.P. Geller, D. Oing, M. Schleberger, A. Di Bartolomeo

We study the effect of electric stress, gas pressure and gas type on the hysteresis in the transfer characteristics of monolayer molybdenum disulfide (MoS2) field effect transistors. The presence of defects and point vacancies in the MoS2 crystal structure facilitates the adsorption of oxygen, nitrogen, hydrogen or methane, which strongly affect the transistor electrical characteristics. Although the gas adsorption does not modify the conduction type, we demonstrate a correlation between hysteresis width and adsorption energy onto the MoS2 surface. We show that hysteresis is controllable by pressure and/or gas type. Hysteresis features two well-separated current levels, especially when gases are stably adsorbed on the channel, which can be exploited in memory devices.


Anisotropy in the dielectric function of Bi$_2$Te$_3$ from first principles: From the UV-visible to the infrared range. (arXiv:2306.15398v1 [cond-mat.mtrl-sci])
R. Busselez, A. Levchuk, P. Ruello, V. Juvé, B. Arnaud

The dielectric properties of Bi$_2$Te$_3$, a layered compound crystallizing in a rhombohedral structure, are investigated by means of first-principles calculations at the random phase approximation level. A special attention is devoted to the anisotropy in the dielectric function and to the local field effects that strongly renormalize the optical properties in the UV-visible range when the electric field is polarized along the stacking axis. Furthermore, both the Born effective charges for each atom and the zone center phonon frequencies and eigenvectors needed to describe the dielectric response in the infrared range are computed. Our theoretical near-normal incidence reflectivity spectras in both the UV-visible and infrared range are in fairly good agreement with the experimental spectras, provided that the free carriers Drude contribution arising from defects is included in the infrared response. The anisotropic plasmon frequencies entering the Drude model are computed within the rigid band approximation, suggesting that a measurement of the reflectivity in the infrared range for both polarizations might allow to infer not only the type of doping but also the level of doping.


Nonlinear intensity dependence of ratchet currents induced by terahertz laser radiation in bilayer graphene with asymmetric periodic grating gates. (arXiv:2306.15405v1 [cond-mat.mes-hall])
Erwin Mönch, Stefan Hubmann, Ivan Yahniuk, Sophia Schweiss, Vasily V. Bel'kov, Leonid E. Golub, Robin Huber, Jonathan Eroms, Kenji Watanabe, Takashi Taniguchi, Dieter Weiss, Sergey D. Ganichev

We report on the observation of a nonlinear intensity dependence of the terahertz radiation induced ratchet effects in bilayer graphene with asymmetric dual grating gate lateral lattices. These nonlinear ratchet currents are studied in structures of two designs with dual grating gate fabricated on top of encapsulated bilayer graphene and beneath it. The strength and sign of the photocurrent can be controllably varied by changing the bias voltages applied to individual dual grating subgates and the back gate. The current consists of contributions insensitive to the radiation's polarization state, defined by the orientation of the radiation electric field vector with respect to the dual grating gate metal stripes, and the circular ratchet sensitive to the radiation helicity. We show that intense terahertz radiation results in a nonlinear intensity dependence caused by electron gas heating. At room temperature the ratchet current saturates at high intensities of the order of hundreds to several hundreds of kWcm$^{-2}$. At $T = 4 {\rm K}$, the nonlinearity manifests itself at intensities that are one or two orders of magnitude lower, moreover, the photoresponse exhibits a complex dependence on the intensity, including a saturation and even a change of sign with increasing intensity. This complexity is attributed to the interplay of the Seebeck ratchet and the dynamic carrier density redistribution, which feature different intensity dependencies and a nonlinear behavior of the sample's conductivity induced by electron gas heating. Our study demonstrates that graphene-based asymmetric dual grating gate devices can be used as terahertz detectors at room temperature over a wide dynamic range, spanning many orders of magnitude of terahertz radiation power. Therefore, their integration together with current-driven read-out electronics is attractive for the operation with high-power pulsed sources.


Realizing efficient topological temporal pumping in electrical circuits. (arXiv:2306.15434v1 [cond-mat.other])
Alexander Stegmaier, Hauke Brand, Stefan Imhof, Alexander Fritzsche, Tobias Helbig, Tobias Hofmann, Igor Boettcher, Martin Greiter, Ching Hua Lee, Gaurav Bahl, Alexander Szameit, Tobias Kießling, Ronny Thomale, Lavi K. Upreti

Quantized adiabatic transport can occur when a system is slowly modulated over time. In most realizations however, the efficiency of such transport is reduced by unwanted dissipation, back-scattering, and non-adiabatic effects. In this work, we realize a topological adiabatic pump in an electrical circuit network that supports remarkably stable and long-lasting pumping of a voltage signal. We further characterize the topology of our system by deducing the Chern number from the measured edge band structure. To achieve this, the experimental setup makes use of active circuit elements that act as time-variable voltage-controlled inductors.


Two-dimensional few-atom noble gas clusters in a graphene sandwich. (arXiv:2306.15436v1 [cond-mat.mes-hall])
Manuel Längle, Kenichiro Mizohat, Clemens Mangler, Alberto Trentino, Kimmo Mustonen, E. Harriet Åhlgren, Jani Kotakoski

Van der Waals atomic solids of noble gases on metals at cryogenic temperatures were the first experimental examples of two-dimensional systems. Recently such structures have also been created on under encapsulation by graphene, allowing studies at elevated temperatures through scanning tunneling microscopy. However, for this technique, the encapsulation layer often obscures the actual arrangement of the noble gas atoms. Here, we create Kr and Xe clusters in between two suspended graphene layers, and uncover their atomic structure through direct imaging with transmission electron microscopy. We show that small crystals (N<9) arrange as expected based on the simple non-directional van der Waals interaction. Crystals larger than this show some deviations for the outermost atoms, possibly enabled by deformations in the encapsulating graphene lattice. We further discuss the dynamics of the clusters within the graphene sandwich, and show that while all Xe clusters with up to at least N=51 remain solid, Kr clusters with already N~16 turn occasionally fluid under our experimental conditions with an estimated pressure of ca. 0.3 GPa. This study opens a way for the so-far unexplored frontier of encapsulated two-dimensional van der Waals solids with exciting possibilities for condensed matter physics research that expands from quantum structures to biological applications.


Synthetic gauge fields enable high-order topology on Brillouin real projective plane. (arXiv:2306.15477v1 [cond-mat.mes-hall])
Hu Jinbing, Zhuang Songlin, Yang Yi

The topology of the Brillouin zone, foundational in topological physics, is always assumed to be a torus. We theoretically report the construction of Brillouin real projective plane ($\mathrm{RP}^2$) and the appearance of quadrupole insulating phase, which are enabled by momentum-space nonsymmorphic symmetries stemming from $\mathbb{Z}_2$ synthetic gauge fields. We show that the momentum-space nonsymmorphic symmetries quantize bulk polarization and Wannier-sector polarization nonlocally across different momenta, resulting in quantized corner charges and an isotropic binary bulk quadrupole phase diagram, where the phase transition is triggered by a bulk energy gap closing. Under open boundary conditions, the nontrivial bulk quadrupole phase manifests either trivial or nontrivial edge polarization, resulting from the violation of momentum-space nonsymmorphic symmetries under lattice termination. We present a concrete design for the $\mathrm{RP}^2$ quadrupole insulator based on acoustic resonator arrays and discuss its feasibility in optics, mechanics, and electrical circuits. Our results show that deforming the Brillouin manifold creates opportunities for realizing high-order band topology.


Laser induced surface magnetization in Floquet-Weyl semimetals. (arXiv:2306.15522v1 [cond-mat.mtrl-sci])
Runnan Zhang, Ken-ichi Hino, Nobuya Maeshima, Haruki Yogemura, Takeru Karikomi

We investigate optically induced magnetization in Floquet-Weyl semimetals generated by irradiation of a circularly-polarized continuous-wave laser from the group II-V narrow gap semiconductor Zn$_3$As$_2$ in a theoretical manner. Here, this trivial and nonmagnetic crystal is driven by the laser with a nearly resonant frequency with a band gap to generate two types of Floquet-Weyl semimetal phases composed of different spin states. These two phases host nontrivial two-dimensional surface states pinned to the respective pairs of the Weyl points. By numerically evaluating the laser-induced transient carrier-dynamics, it is found that both spins are distributed in an uneven manner on the corresponding surface states, respectively, due to significantly different excitation probabilities caused by the circularly-polarized laser with the nearly resonant frequency. It is likely that such spin-polarized surface states produce surface magnetization, and furthermore the inverse Faraday effect also contributes almost as much as the spin magnetization. To be more specific, excited carries with high density of the order of $10^{21}\: {\rm cm}^{-3}$ are generated by the laser with electric field strength of a few MV/cm to result in the surface magnetization that becomes asymptotically constant with respect to time, around 1 mT. The magnitude and the direction of it depend sharply on both of the intensity and frequency of the driving laser, which would be detected by virtue of the magneto-optic Kerr effect.


Charge-resolved entanglement in the presence of topological defects. (arXiv:2306.15532v1 [quant-ph])
David X. Horvath, Shachar Fraenkel, Stefano Scopa, Colin Rylands

Topological excitations or defects such as solitons are ubiquitous throughout physics, supporting numerous interesting phenomena like zero energy modes with exotic statistics and fractionalized charges. In this paper, we study such objects through the lens of symmetry-resolved entanglement entropy. Specifically, we compute the charge-resolved entanglement entropy for a single interval in the low-lying states of the Su-Schrieffer-Heeger model in the presence of topological defects. Using a combination of exact and asymptotic analytic techniques, backed up by numerical analysis, we find that, compared to the unresolved counterpart and to the pure system, a richer structure of entanglement emerges. This includes a redistribution between its configurational and fluctuational parts due to the presence of the defect and an interesting interplay with entanglement equipartition. In particular, in a subsystem that excludes the defect, equipartition is restricted to charge sectors of the same parity, while full equipartition is restored only if the subsystem includes the defect, as long as the associated zero mode remains unoccupied. Additionally, by exciting zero modes in the presence of multiple defects, we observe a significant enhancement of entanglement in certain charge sectors, due to charge splitting on the defects. These constitute two different scenarios featuring the rare breakdown of entanglement equipartition. We unveil the joint mechanism underlying these two scenarios by relating them to degeneracies in the spectrum of the charge-resolved entanglement Hamiltonian.


The Radial Hedgehog Solution in the Landau-de Gennes Theory: Effects of the Bulk Potentials. (arXiv:2306.15563v1 [cond-mat.soft])
Sophie McLauchlan, Yucen Han, Matthias Langer, Apala Majumdar

We study equilibrium configurations in spherical droplets of nematic liquid crystal with strong radial anchoring, within the Landau-de Gennes theory with a sixth-order bulk potential. The sixth-order potential predicts a bulk biaxial phase for sufficiently low temperatures, which the conventional fourth-order potential cannot predict. We prove the existence of a radial hedgehog solution, which is a uniaxial solution with a single isotropic point defect at the droplet centre, for all temperatures and droplet sizes, and prove that there is a unique radial hedgehog solution for moderately low temperatures, but not deep in the nematic phase. We numerically compute critical points of the Landau-de Gennes free energy with the sixth order bulk potential, with rotational and mirror symmetry, and find at least two competing stable critical points: the biaxial torus and split core solutions, which have biaxial regions around the centre, for low temperatures. The size of the biaxial regions increases with decreasing temperature. We also compare the properties of the radial hedgehog solution with the fourth-order and sixth-order potentials respectively, in terms of the Morse indices as a function of the temperature and droplet radius; the role of the radial hedgehog solution as a transition state in switching processes; and compare the bifurcation plots with temperature, with the fourth- and sixth-order potentials. Overall, the sixth-order potential has a stabilising effect on biaxial critical points and a de-stabilising effect on uniaxial critical points and we discover an altogether novel bulk biaxial critical point of the Landau-de Gennes energy with the sixth-order potential, for which the bulk biaxiality is driven by the sixth-order potential.


Reliability and operation cost of underdamped memories during cyclic erasures. (arXiv:2306.15573v1 [cond-mat.stat-mech])
Salambô Dago, Sergio Ciliberto, Ludovic Bellon

The reliability of fast repeated erasures is studied experimentally and theoretically in a 1-bit underdamped memory. The bit is encoded by the position of a micro-mechanical oscillator whose motion is confined in a double well potential. To contain the energetic cost of fast erasures, we use a resonator with high quality factor $Q$: the erasure work $\mathcal{W}$ is close to Landauer's bound, even at high speed. The drawback is the rise of the system's temperature $T$ due to a weak coupling to the environment. Repeated erasures without letting the memory thermalize between operations result in a continuous warming, potentially leading to a thermal noise overcoming the barrier between the potential wells. In such case, the reset operation can fail to reach the targeted logical state. The reliability is characterized by the success rate $R^{\textrm{s}}_i$ after $i$ successive operations. $\mathcal{W}$, $T$ and $R^{\textrm{s}}_i$ are studied experimentally as a function of the erasure speed. Above a velocity threshold, $T$ soars while $R^{\textrm{s}}_i$ collapses: the reliability of too fast erasures is low. These experimental results are fully justified by two complementary models. We demonstrate that $Q\simeq 10$ is optimal to contain energetic costs and maintain high reliability standards for repeated erasures at any speed.


The cold-atom elevator: From edge-state injection to the preparation of fractional Chern insulators. (arXiv:2306.15610v1 [cond-mat.quant-gas])
Botao Wang, Monika Aidelsburger, Jean Dalibard, André Eckardt, Nathan Goldman

Optical box traps for cold atoms offer new possibilities for quantum-gas experiments. Building on their exquisite spatial and temporal control, we propose to engineer system-reservoir configurations using box traps, in view of preparing and manipulating topological atomic states in optical lattices. First, we consider the injection of particles from the reservoir to the system: this scenario is shown to be particularly well suited to activate energy-selective chiral edge currents, but also, to prepare fractional Chern insulating ground states. Then, we devise a practical evaporative-cooling scheme to effectively cool down atomic gases into topological ground states. Our open-system approach to optical-lattice settings provides a new path for the investigation of ultracold quantum matter, including strongly-correlated and topological phases.


Incommensurate Magnetic Order in the $\mathbb{Z}_2$ Kagome Metal GdV$_6$Sn$_6$. (arXiv:2306.15613v1 [cond-mat.str-el])
Zach Porter, Ganesh Pokharel, Jong-Woo Kim, Phillip J. Ryan, Stephen D. Wilson

We characterize the magnetic ground state of the topological kagome metal GdV$_6$Sn$_6$ via resonant X-ray diffraction. Previous magnetoentropic studies of GdV$_6$Sn$_6$ suggested the presence of a modulated magnetic order distinct from the ferromagnetism that is easily polarized by the application of a magnetic field. Diffraction data near the Gd-$L_2$ edge directly resolve a $c$-axis modulated spin structure order on the Gd sublattice with an incommensurate wave vector that evolves upon cooling toward a partial lock-in transition. While equal moment (spiral) and amplitude (sine) modulated spin states can not be unambiguously discerned from the scattering data, the overall phenomenology suggests an amplitude modulated state with moments predominantly oriented in the $ab$-plane. Comparisons to the ``double-flat" spiral state observed in Mn-based $R$Mn$_6$Sn$_6$ kagome compounds of the same structure type are discussed.


Unveiling the orbital-selective electronic band reconstruction through the structural phase transition in TaTe$_2$. (arXiv:2306.15627v1 [cond-mat.str-el])
Natsuki Mitsuishi, Yusuke Sugita, Tomoki Akiba, Yuki Takahashi, Masato Sakano, Koji Horiba, Hiroshi Kumigashira, Hidefumi Takahashi, Shintaro Ishiwata, Yukitoshi Motome, Kyoko Ishizaka

Tantalum ditelluride TaTe$_2$ belongs to the family of layered transition metal dichalcogenides but exhibits a unique structural phase transition at around 170 K that accompanies the rearrangement of the Ta atomic network from a "ribbon chain" to a "butterfly-like" pattern. While multiple mechanisms including Fermi surface nesting and chemical bonding instabilities have been intensively discussed, the origin of this transition remains elusive. Here we investigate the electronic structure of single-crystalline TaTe$_2$ with a particular focus on its modifications through the phase transition, by employing core-level and angle-resolved photoemission spectroscopy combined with first-principles calculations. Temperature-dependent core-level spectroscopy demonstrates a splitting of the Ta $4f$ core-level spectra through the phase transition indicative of the Ta-dominated electronic state reconstruction. Low-energy electronic state measurements further reveal an unusual kink-like band reconstruction occurring at the Brillouin zone boundary, which cannot be explained by Fermi surface nesting or band folding effects. On the basis of the orbital-projected band calculations, this band reconstruction is mainly attributed to the modifications of specific Ta $5d$ states, namely the $d_{XY}$ orbitals (the ones elongating along the ribbon chains) at the center Ta sites of the ribbon chains. The present results highlight the strong orbital-dependent electronic state reconstruction through the phase transition in this system and provide fundamental insights towards understanding complex electron-lattice-bond coupled phenomena.


Utilizing multimodal microscopy to reconstruct Si/SiGe interfacial atomic disorder and infer its impacts on qubit variability. (arXiv:2306.15646v1 [cond-mat.mtrl-sci])
Luis Fabián Peña, Justine C. Koepke, J. Houston Dycus, Andrew Mounce, Andrew D. Baczewski, N. Tobias Jacobson, Ezra Bussmann

SiGe heteroepitaxial growth yields pristine host material for quantum dot qubits, but residual interface disorder can lead to qubit-to-qubit variability that might pose an obstacle to reliable SiGe-based quantum computing. We demonstrate a technique to reconstruct 3D interfacial atomic structure spanning multiqubit areas by combining data from two verifiably atomic-resolution microscopy techniques. Utilizing scanning tunneling microscopy (STM) to track molecular beam epitaxy (MBE) growth, we image surface atomic structure following deposition of each heterostructure layer revealing nanosized SiGe undulations, disordered strained-Si atomic steps, and nonconformal uncorrelated roughness between interfaces. Since phenomena such as atomic intermixing during subsequent overgrowth inevitably modify interfaces, we measure post-growth structure via cross-sectional high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Features such as nanosized roughness remain intact, but atomic step structure is indiscernible in $1.0\pm 0.4$~nm-wide intermixing at interfaces. Convolving STM and HAADF-STEM data yields 3D structures capturing interface roughness and intermixing. We utilize the structures in an atomistic multivalley effective mass theory to quantify qubit spectral variability. The results indicate (1) appreciable valley splitting (VS) variability of roughly $\pm$ $50\%$ owing to alloy disorder, and (2) roughness-induced double-dot detuning bias energy variability of order $1-10$ meV depending on well thickness. For measured intermixing, atomic steps have negligible influence on VS, and uncorrelated roughness causes spatially fluctuating energy biases in double-dot detunings potentially incorrectly attributed to charge disorder.


Thermopower in an anisotropic two-dimensional Weyl semimetal. (arXiv:1811.04952v4 [cond-mat.mes-hall] UPDATED)
Ipsita Mandal, Kush Saha

We investigate the generation of an electric current from a temperature gradient in a two-dimensional Weyl semimetal with anisotropy, in both the presence and absence of a quantizing magnetic field. We show that the anisotropy leads to doping dependences of thermopower and thermal conductivities which are different from those in isotropic Dirac materials. Additionally, we find that a quantizing magnetic field in such systems leads to an interesting magnetic field dependence of the longitudinal thermopower, resulting in unsaturated thermoelectric coefficients. Thus the results presented here will serve as a guide to achieving high thermopower and a thermoelectric figure-of-merit in graphene-based materials, as well as organic conductors such as $\alpha$-(BEDT-TTF)$_2$I$_3$.


Emergent Disorder and Mechanical Memory in Periodic Metamaterials. (arXiv:2204.04000v5 [cond-mat.soft] UPDATED)
Chaviva Sirote-Katz, Dor Shohat, Carl Merrigan, Yoav Lahini, Cristiano Nisoli, Yair Shokef

Ordered mechanical systems typically have one or only a few stable rest configurations, and hence are not considered useful for encoding memory. Multistable and history-dependent responses usually emerge from quenched disorder, for example in amorphous solids or crumpled sheets. In contrast, due to geometric frustration, periodic magnetic systems can create their own disorder and espouse an extensive manifold of quasi-degenerate configurations. Inspired by the topological structure of frustrated artificial spin ices, we introduce an approach to design ordered, periodic mechanical metamaterials that exhibit an extensive set of spatially disordered states. While our design exploits the correspondence between frustration in magnetism and incompatibility in meta-mechanics, our mechanical systems encompass continuous degrees of freedom, and are hence richer than their magnetic counterparts. We show how such systems exhibit non-Abelian and history-dependent responses, as their state can depend on the order in which external manipulations were applied. We demonstrate how this richness of the dynamics enables to recognize, from a static measurement of the final state, the sequence of operations that an extended system underwent. Thus, multistability and potential to perform computation emerge from geometric frustration in ordered mechanical lattices that create their own disorder.


A Tale of Two Quantum Compass Models. (arXiv:2206.15199v4 [cond-mat.str-el] UPDATED)
Soumya Sur, M. S. Laad, Arya Subramonian, S. R. Hassan

We investigate two variants of quantum compass models (QCMs). The first, an orbital-only honeycomb QCM, is shown to exhibit a quantum phase transition (QPT) from a $XX$- to $ZZ$-ordered phase in the $3d$-Ising universality class, in accord with earlier studies. In a fractionalized parton construction, this describes a ``superfluid-Mott insulator'' transition between a higher-order topological superfluid and the toric code, the latter described as a $p$-wave resonating valence bond state of the partons. The second variant, the spinless fermion QCM on a square lattice, is of interest in the context of cold-atom lattices with higher-angular momentum states on each atom. We explore finite-temperature orbital order-disorder transitions in the itinerant and localized limits using complementary methods. In the itinerant limit, we uncover an intricate temperature ($T$)-dependent dimensional crossover from a high-$T$ quasi-$1d$ insulator-like state, via an incoherent bad-metal-like state at intermediate $T$, to a $2d$ symmetry-broken insulator at low $T$, well below the ``orbital'' ordering scale. Finally, we discuss how engineering specific, tunable, and realistic perturbations in both these variants can act as a playground for simulating a variety of exotic QPTs between topologically ordered and trivial phases. In the cold-atom context, we propose a novel way to engineer a possible realisation of the exotic exciton Bose liquid phase at a QPT between a Bose superfluid and a charge density wave insulator. We argue that advances in the design of Josephson junction arrays and manipulating cold-atom lattices offer the hope of simulating such novel phases of matter in the foreseeable future.


Topological Monomodes in non-Hermitian Systems. (arXiv:2304.05748v2 [cond-mat.mes-hall] UPDATED)
E. Slootman, W. Cherifi, L. Eek, R. Arouca, E. J. Bergholtz, M. Bourennane, C. Morais Smith

Topological monomodes have been for long as elusive as magnetic monopoles. The latter was experimentally shown to emerge in effective descriptions of condensed-matter systems, while the experimental exploration of the former has largely been hindered by the complexity of the conceived setups. Here, we present a remarkably simple model and the experimental observation of topological monomodes generated dynamically. By focusing on non-Hermitian one-dimensional (1D) and 2D Su-Schrieffer-Heeger (SSH) models, we theoretically unveil the minimal configuration to realize a topological monomode upon engineering losses and breaking of lattice symmetries. Furthermore, we classify the systems in terms of the (non-Hermitian) symmetries that are present and calculate the corresponding topological invariants. To corroborate the theory, we present experiments in photonic lattices, in which a monomode is observed in the non-Hermitian 1D and 2D SSH models, thus breaking the paradigm that topological corner states should appear in pairs. Our findings might have profound implications for photonics and quantum optics because topological monomodes increase the robustness of corner states by preventing recombination.


Symmetry Fractionalized (Irrationalized) Fusion Rules and Two Domain-Wall Verlinde Formulae. (arXiv:2304.08475v2 [cond-mat.str-el] UPDATED)
Yu Zhao, Hongyu Wang, Yuting Hu, Yidun Wan

We investigate the composite systems consisting of topological orders separated by gapped domain walls. We derive a pair of domain-wall Verlinde formulae, that elucidate the connection between the braiding of interdomain excitations labeled by pairs of anyons in different domains and quasiparticles in the gapped domain wall with their respective fusion rules. Through explicit non-Abelian examples, we showcase the calculation of such braiding and fusion, revealing that the fusion rules for interdomain excitations are generally fractional or irrational. By investigating the correspondence between composite systems and anyon condensation, we unveil the reason for designating these fusion rules as symmetry fractionalized (irrationalized) fusion rules. Our findings hold promise for applications across various fields, such as topological quantum computation, topological field theory, and conformal field theory.


Topologically-constrained fluctuations and thermodynamics regulate nonequilibrium response. (arXiv:2305.19348v3 [cond-mat.stat-mech] UPDATED)
Gabriela Fernandes Martins, Jordan M. Horowitz

Limits on a system's response to external perturbations inform our understanding of how physical properties can be shaped by microscopic characteristics. Here, we derive constraints on the steady-state nonequilibrium response of physical observables in terms of the topology of the microscopic state space and the strength of thermodynamic driving. Notably, evaluation of these limits requires no kinetic information beyond the state-space structure. When applied to models of receptor binding, we find that sensitivity is bounded by the steepness of a Hill function with a Hill coefficient enhanced by the chemical driving beyond the structural equilibrium limit.


On the detection of collective modes in unconventional superconductors using tunneling spectroscopy. (arXiv:2306.00072v2 [cond-mat.supr-con] UPDATED)
Patrick A. Lee, Jacob F. Steiner

We propose using tunneling spectroscopy with a superconducting electrode to probe the collective modes of unconventional superconductors. The modes are predicted to appear as peaks in dI/dV at voltages given by eV = {\omega}i/2 where {\omega}i denotes the mode frequencies. This may prove to be a powerful tool to investigate the pairing symmetry of unconventional superconductors. The peaks associated with the collective modes appear at fourth order in the single particle tunneling matrix element. At the same fourth order, multiple Andreev reflection (MAR) leads to peaks at voltage equal to the energy gaps, which, in BCS superconductors, coincides with the expected position of the amplitude (Higgs) mode. The peaks stemming from the collective modes of unconventional superconductors do not suffer from this coincidence. For scanning tunneling microscopes (STM), we estimate that the magnitude of the collective mode contribution is smaller than the MAR contribution by the ratio of the energy gap to the Fermi energy. Moreover, there is no access to the mode dispersion. Conversely, for planar tunnel junctions the collective mode peak is expected to dominate over the MAR peak, and the mode dispersion can be measured. We discuss systems where the search for such collective modes is promising.


Nonlinear dynamics of skyrmion strings. (arXiv:2306.11866v2 [nlin.PS] UPDATED)
Volodymyr P. Kravchuk

The skyrmion core, percolating the volume of the magnet, forms a skyrmion string -- the topological Dirac-string-like object. Here we analyze the nonlinear dynamics of skyrmion string in a low-energy regime by means of the collective variables approach which we generalized for the case of strings. Using the perturbative method of multiple scales (both in space and time), we show that the weakly nonlinear dynamics of the translational mode propagating along the string is captured by the nonlinear Schroedinger equation of the focusing type. As a result, the basic "planar-wave" solution, which has a form of a helix-shaped wave, experiences modulational instability. The latter leads to the formation of cnoidal waves. Both types of cnoidal waves, dn- and cn-waves, as well as the separatrix soliton solution, are confirmed by the micromagnetic simulations. Beyond the class of the traveling-wave solutions, we found Ma-breather propagating along the string. Finally, we proposed a generalized approach, which enables one to describe nonlinear dynamics of the modes of different symmetries, e.g. radially symmetrical or elliptical.


Lifshitz transitions and angular conductivity diagrams in metals with complex Fermi surfaces. (arXiv:2306.12225v2 [cond-mat.mtrl-sci] UPDATED)
A. Ya. Maltsev

We consider the Lifshitz topological transitions and the corresponding changes in the galvanomagnetic properties of a metal from the point of view of the general classification of open electron trajectories arising on Fermi surfaces of arbitrary complexity in the presence of magnetic field. The construction of such a classification is the content of the Novikov problem and is based on the division of non-closed electron trajectories into topologically regular and chaotic trajectories. The description of stable topologically regular trajectories gives a basis for a complete classification of non-closed trajectories on arbitrary Fermi surfaces and is connected with special topological structures on these surfaces. Using this description, we describe here the distinctive features of possible changes in the picture of electron trajectories during the Lifshitz transitions, as well as changes in the conductivity behavior in the presence of a strong magnetic field. As it turns out, the use of such an approach makes it possible to describe not only the changes associated with stable electron trajectories, but also the most general changes of the conductivity diagram in strong magnetic fields.


Found 8 papers in prb
Date of feed: Wed, 28 Jun 2023 03:17:04 GMT

Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)

Nodal-line resonance generating the giant anomalous Hall effect of ${\mathrm{Co}}_{3}{\mathrm{Sn}}_{2}{\mathrm{S}}_{2}$
F. Schilberth, M.-C. Jiang, S. Minami, M. A. Kassem, F. Mayr, T. Koretsune, Y. Tabata, T. Waki, H. Nakamura, G.-Y. Guo, R. Arita, I. Kézsmárki, and S. Bordács
Author(s): F. Schilberth, M.-C. Jiang, S. Minami, M. A. Kassem, F. Mayr, T. Koretsune, Y. Tabata, T. Waki, H. Nakamura, G.-Y. Guo, R. Arita, I. Kézsmárki, and S. Bordács

Giant anomalous Hall effect (AHE) and magneto-optical activity can emerge in magnets with topologically nontrivial degeneracies. However, identifying the specific band-structure features such as Weyl points, nodal lines, or planes which generate the anomalous response is a challenging issue. Since t…


[Phys. Rev. B 107, 214441] Published Tue Jun 27, 2023

Softening of Majorana edge states by long-range couplings
Alessandro Tarantola and Nicolò Defenu
Author(s): Alessandro Tarantola and Nicolò Defenu

The inclusion of long-range couplings in the Kitaev chain is shown to modify the universal scaling of topological states close to the critical point. By means of the scattering approach, we prove that the Majorana states soften, becoming increasingly delocalized at a universal rate which is only det…


[Phys. Rev. B 107, 235146] Published Tue Jun 27, 2023

Boosting the surface conduction in a topological insulator
M. Taupin, G. Eguchi, M. Lužnik, A. Steiger-Thirsfeld, Y. Ishida, K. Kuroda, S. Shin, A. Kimura, and S. Paschen
Author(s): M. Taupin, G. Eguchi, M. Lužnik, A. Steiger-Thirsfeld, Y. Ishida, K. Kuroda, S. Shin, A. Kimura, and S. Paschen

The protected surface conduction of topological insulators is in high demand for the next generation of electronic devices. What is needed to move forward are robust settings where topological surface currents can be controlled by simple means, ideally by the application of external stimuli. Surpris…


[Phys. Rev. B 107, 235306] Published Tue Jun 27, 2023

Twist-induced interlayer charge buildup in a $\mathrm{W}{\mathrm{S}}_{2}$ bilayer revealed by electron Compton scattering and density functional theory
A. Talmantaite, Y. Xie, A. Cohen, P. K. Mohapatra, A. Ismach, T. Mizoguchi, S. J. Clark, and B. G. Mendis
Author(s): A. Talmantaite, Y. Xie, A. Cohen, P. K. Mohapatra, A. Ismach, T. Mizoguchi, S. J. Clark, and B. G. Mendis

Exotic properties emerge from the electronic structure of few-layer transition-metal dichalcogenides (TMDs), such as direct band gaps in monolayers and moiré excitons in twisted bilayers, which are exploited in modern optoelectronic devices and twistronics. Here, Compton scattering in a transmission…


[Phys. Rev. B 107, 235424] Published Tue Jun 27, 2023

Intrinsically multilayer moiré heterostructures
Aaron Dunbrack and Jennifer Cano
Author(s): Aaron Dunbrack and Jennifer Cano

We introduce trilayer and multilayer moiré heterostructures that cannot be viewed from the “moiré-of-moiré” perspective of helically twisted trilayer graphene. These “intrinsically trilayer” moiré systems feature periodic modulation of a local quasicrystalline structure. They open the door to realiz…


[Phys. Rev. B 107, 235425] Published Tue Jun 27, 2023

Layer-resolved resonance intensity of evanescent polariton modes in anisotropic multilayers
Nikolai Christian Passler, Xiang Ni, Giulia Carini, Dmitry N. Chigrin, Andrea Alù, and Alexander Paarmann
Author(s): Nikolai Christian Passler, Xiang Ni, Giulia Carini, Dmitry N. Chigrin, Andrea Alù, and Alexander Paarmann

Phonon polariton modes in layered anisotropic heterostructures are a key building block for modern nanophotonic technologies. The light-matter interaction for evanescent excitation of such a multilayer system can be theoretically described by a transfer-matrix formalism. This method allows us to com…


[Phys. Rev. B 107, 235426] Published Tue Jun 27, 2023

Large Nernst effect and possible temperature-induced Lifshitz transition in topological semimetal ${\mathrm{YbMnSb}}_{2}$
Sheng Xu, Chenxi Jiang, Shu-Xiang Li, Jun-Jian Mi, Zheng Li, Tian-Long Xia, Qian Tao, and Zhu-An Xu
Author(s): Sheng Xu, Chenxi Jiang, Shu-Xiang Li, Jun-Jian Mi, Zheng Li, Tian-Long Xia, Qian Tao, and Zhu-An Xu

Topological materials provide an interesting platform in the study of thermoelectric effect due to their novel electronic properties. Here we report the magneto-Seebeck (MS) effect, large Nernst effect, and a possible temperature-induced Lifshitz transition in topological semimetal ${\mathrm{YbMnSb}…


[Phys. Rev. B 107, 245138] Published Tue Jun 27, 2023

Electronic structure of biased alternating-twist multilayer graphene
Kyungjin Shin, Yunsu Jang, Jiseon Shin, Jeil Jung, and Hongki Min
Author(s): Kyungjin Shin, Yunsu Jang, Jiseon Shin, Jeil Jung, and Hongki Min

We theoretically study the energy and optical absorption spectra of alternating-twist multilayer graphene (ATMG) under a perpendicular electric field. We obtain analytically the low-energy effective Hamiltonian of ATMG up to pentalayer in the presence of the interlayer bias by means of first-order d…


[Phys. Rev. B 107, 245139] Published Tue Jun 27, 2023

Found 1 papers in pr_res
Date of feed: Wed, 28 Jun 2023 03:17:04 GMT

Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)

Particle acceleration at magnetized, relativistic, turbulent shock fronts
Virginia Bresci, Martin Lemoine, and Laurent Gremillet
Author(s): Virginia Bresci, Martin Lemoine, and Laurent Gremillet

The efficiency of particle acceleration at shock waves in relativistic, magnetized astrophysical outflows is a debated topic with far-reaching implications. Here, we study the impact of well-developed turbulence in the pre-shock plasma. Our simulations demonstrate that, for a mildly relativistic mag…


[Phys. Rev. Research 5, 023194] Published Tue Jun 27, 2023

Found 2 papers in nano-lett
Date of feed: Tue, 27 Jun 2023 21:05:31 GMT

Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)

[ASAP] Atomic-Scale Mechanisms of MoS2 Oxidation for Kinetic Control of MoS2/MoO3 Interfaces
Kate Reidy, Wouter Mortelmans, Seong Soon Jo, Aubrey N. Penn, Alexandre C. Foucher, Zhenjing Liu, Tao Cai, Baoming Wang, Frances M. Ross, and R. Jaramillo

TOC Graphic

Nano Letters
DOI: 10.1021/acs.nanolett.3c00303

[ASAP] Ab Initio Spin Hamiltonian and Topological Noncentrosymmetric Magnetism in Twisted Bilayer CrI3
Kyoung-Min Kim, Do Hoon Kiem, Grigory Bednik, Myung Joon Han, and Moon Jip Park

TOC Graphic

Nano Letters
DOI: 10.1021/acs.nanolett.3c01529

Found 2 papers in acs-nano
Date of feed: Tue, 27 Jun 2023 20:47:10 GMT

Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)

[ASAP] Role of Bilayer Graphene Microstructure on the Nucleation of WSe2 Overlayers
Saiphaneendra Bachu, Malgorzata Kowalik, Benjamin Huet, Nadire Nayir, Swarit Dwivedi, Danielle Reifsnyder Hickey, Chenhao Qian, David W. Snyder, Slava V. Rotkin, Joan M. Redwing, Adri C. T. van Duin, and Nasim Alem

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ACS Nano
DOI: 10.1021/acsnano.2c12621

[ASAP] MoS2‑Plasmonic Nanocavities for Raman Spectra of Single Extracellular Vesicles Reveal Molecular Progression in Glioblastoma
Mahsa Jalali, Carolina del Real Mata, Laura Montermini, Olivia Jeanne, Imman I.Hosseini, Zonglin Gu, Cristiana Spinelli, Yao Lu, Nadim Tawil, Marie Christine Guiot, Zhi He, Sebastian Wachsmann-Hogiu, Ruhong Zhou, Kevin Petrecca, Walter W. Reisner, Janusz Rak, and Sara Mahshid⊗

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ACS Nano
DOI: 10.1021/acsnano.2c09222

Found 1 papers in nat-comm


Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)

Interspecies exciton interactions lead to enhanced nonlinearity of dipolar excitons and polaritons in MoS2 homobilayers
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