Found 29 papers in cond-mat
Date of feed: Thu, 24 Aug 2023 00:30:00 GMT

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Anomalies of Non-Invertible Symmetries in (3+1)d. (arXiv:2308.11706v1 [hep-th])
Clay Cordova, Po-Shen Hsin, Carolyn Zhang

Anomalies of global symmetries are important tools for understanding the dynamics of quantum systems. We investigate anomalies of non-invertible symmetries in 3+1d using 4+1d bulk topological quantum field theories given by Abelian two-form gauge theories, with a 0-form permutation symmetry. Gauging the 0-form symmetry gives the 4+1d "inflow" symmetry topological field theory for the non-invertible symmetry. We find a two levels of anomalies: (1) the bulk may fail to have an appropriate set of loop excitations which can condense to trivialize the boundary dynamics, and (2) the "Frobenius-Schur indicator" of the non-invertible symmetry (generalizing the Frobenius-Schur indicator of 1+1d fusion categories) may be incompatible with trivial boundary dynamics. As a consequence we derive conditions for non-invertible symmetries in 3+1d to be compatible with symmetric gapped phases, and invertible gapped phases. Along the way, we see that the defects characterizing $\mathbb{Z}_{4}$ ordinary symmetry host worldvolume theories with time-reversal symmetry $\mathsf{T}$ obeying the algebra $\mathsf{T}^{2}=C$ or $\mathsf{T}^{2}=(-1)^{F}C,$ with $C$ a unitary charge conjugation symmetry. We classify the anomalies of this symmetry algebra in 2+1d and further use these ideas to construct 2+1d topological orders with non-invertible time-reversal symmetry that permutes anyons. As a concrete realization of our general discussion, we construct new lattice Hamiltonian models in 3+1d with non-invertible symmetry, and constrain their dynamics.

Coulomb drag in metallic twisted bilayer graphene. (arXiv:2308.11739v1 [cond-mat.mes-hall])
Federico Escudero, Juan Sebastián Ardenghi

Strongly correlated phases in twisted bilayer graphene (TBG) typically arise as transitions from a state in which the system behaves as a normal metal. In such metallic regime, electron-electron interactions usually only play a subleading role in transport measurements, compared to the dominant scattering mechanism. Here, we propose and theoretically study an exception to this based on a Coulomb drag setup between two metallic TBG, separated so that they only couple through many-body interactions. We find that by solely varying the twist angle equally in both TBG, the drag resistivity exhibits a unique maximum as the system crossovers from a degenerate to a nondegenerate regime. When the twist angles in each TBG differ, we find an anomalous drag resistivity characterized by the appearance of multiple peaks. We show that this behavior can be related to the dependence of the rectification function on the twist angle.

Dynamics of K$_2$Ni$_2$(SO$_4$)$_3$ governed by proximity to a 3D spin liquid model. (arXiv:2308.11746v1 [cond-mat.str-el])
M. G. Gonzalez, V. Noculak, A. Sharma, V. Favre, J-R. Soh, A. Magrez, R. Bewley, H. O. Jeschke, J. Reuther, H. M. Rønnow, Y. Iqbal, I. Živković

Quantum spin liquids (QSLs) have become a key area of research in magnetism due to their remarkable properties, such as long-range entanglement, fractional excitations, pinch-point singularities, and topologically protected phenomena. In recent years, the search for QSLs has expanded into the three-dimensional world, where promising features have been found in materials that form pyrochlore and hyper-kagome lattices, despite the suppression of quantum fluctuations due to high dimensionality. One such material is the $S = 1$ K$_2$Ni$_2$(SO$_4$)$_3$ compound, which belongs to the langbeinite family consisting of two interconnected trillium lattices. Although magnetically ordered, K$_2$Ni$_2$(SO$_4$)$_3$ has been found to exhibit a highly dynamical and correlated state which can be driven into a pure quantum spin liquid under magnetic fields of only $B \simeq 4$~T. In this article, we combine inelastic neutron scattering measurements with pseudo-fermion functional renormalization group (PFFRG) and classical Monte Carlo (cMC) calculations to study the magnetic properties of K$_2$Ni$_2$(SO$_4$)$_3$, revealing a high level of agreement between the experiment and theory. We further reveal the origin of the dynamical state in K$_2$Ni$_2$(SO$_4$)$_3$ by studying a larger set of exchange parameters, uncovering an `island of liquidity' around a focal point given by a magnetic network composed of tetrahedra on a trillium lattice.

Symmetry breaking induced insulating electronic state in Pb$_{9}$Cu(PO$_4$)$_6$O. (arXiv:2308.11766v1 [cond-mat.mtrl-sci])
Jiaxi Liu, Tianye Yu, Jiangxu Li, Jiantao Wang, Junwen Lai, Yan Sun, Xing-Qiu Chen, Peitao Liu

The recent experimental claim of room-temperature ambient-pressure superconductivity in a Cu-doped lead-apatite (LK-99) has ignited substantial research interest in both experimental and theoretical domains. Previous collinear density functional theory (DFT) calculations with the inclusion of an on-site Hubbard interaction $U$ consistently predict the presence of flat bands crossing the Fermi level. This is in contrast to DFT plus dynamical mean field theory calculations, which reveal the Mott insulating behavior for the stoichiometric Pb$_{9}$Cu(PO$_4$)$_6$O compound. However, the existing calculations are all based on the $P6_3/m$ structure, which is argued to be not the ground-state structure. Here, we revisit the electronic structure of Pb$_{9}$Cu(PO$_4$)$_6$O with the energetically more favorable $P\bar{3}$ structure, fully taking into account the crystal structure and electronic symmetry breaking. We examine all possible configurations for Cu substituting the Pb sites. Our results show that the doped Cu atoms exhibit a preference for substituting the Pb2 sites than the Pb1 sites. In both cases, the calculated substitutional formation energies are large, indicating the difficulty in incorporating Cu at Pb sites. We find that most of structures with Cu at the Pb2 site tend to exhibit insulating states, while the structures with both two Cu atoms at the Pb1 sites (except one configuration) are predicted to be metallic by magnetically collinear DFT+$U$ calculations. However, when accounting for the electronic symmetry breaking, some Cu-doped configurations (including the one employed in previous DFT+$U$ calculations) become insulating. Our work highlights the importance of symmetry breaking in obtaining correct electronic state for Pb$_{9}$Cu(PO$_4$)$_6$O, thereby reconciling previous collinear DFT+$U$ and DFT+DMFT calculations.

Ferromagnetic and insulating behavior in both half magnetic levitation and non-levitation LK-99 like samples. (arXiv:2308.11768v1 [cond-mat.supr-con])
Pinyuan Wang, Xiaoqi Liu, Jun Ge, Chengcheng Ji, Haoran Ji, Yanzhao Liu, Yiwen Ai, Gaoxing Ma, Shichao Qi, Jian Wang

Finding materials exhibiting superconductivity at room temperature has long been one of the ultimate goals in physics and material science. Recently, room-temperature superconducting properties have been claimed in a copper substituted lead phosphate apatite (Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O, or called LK-99) [1-3]. Using a similar approach, we have prepared LK-99 like samples and confirmed the half-levitation behaviors in some small specimens under the influence of a magnet at room temperature. To examine the magnetic properties of our samples, we have performed systematic magnetization measurements on the as-grown LK-99-like samples, including the half-levitated and non-levitated samples. The magnetization measurements show the coexistence of soft-ferromagnetic and diamagnetic signals in both half-levitated and non-levitated samples. The electrical transport measurements on the as-grown LK-99-like samples including both half-levitated and non-levitated samples show an insulating behavior characterized by the increasing resistivity with the decreasing temperature.

Magnetic Skyrmion: From Fundamental Physics to Pioneering Applications. (arXiv:2308.11811v1 [cond-mat.mes-hall])
Kishan K. Mishra, Aijaz H. Lone, Srikant Srinivasan, Hossein Fariborzi, Gianluca Setti

Skyrmionic devices exhibit energy-efficient and high-integration data storage and computing capabilities due to their small size, topological protection, and low drive current requirements. So, to realize these devices, an extensive study, from fundamental physics to practical applications, becomes essential. In this article, we present an exhaustive review of the advancements in understanding the fundamental physics behind magnetic skyrmions and the novel data storage and computing technologies based on them. We begin with an in-depth discussion of fundamental concepts such as topological protection, stability, statics and dynamics essential for understanding skyrmions, henceforth the foundation of skyrmion technologies. For the realization of CMOS-compatible skyrmion functional devices, the writing and reading of the skyrmions are crucial. We discuss the developments in different writing schemes such as STT, SOT, and VCMA. The reading of skyrmions is predominantly achieved via two mechanisms: the Magnetoresistive Tunnel Junction (MTJ) TMR effect and topological resistivity (THE). So, a thorough investigation into the Skyrmion Hall Effect, topological properties, and emergent fields is also provided, concluding the discussion on skyrmion reading developments. Based on the writing and reading schemes, we discuss the applications of the skyrmions in conventional logic, unconventional logic, memory applications, and neuromorphic computing in particular. Subsequently, we present an overview of the potential of skyrmion-hosting Majorana Zero Modes (MZMs) in the emerging Topological Quantum Computation and helicity-dependent skyrmion qubits.

MBD+C: how to incorporate metallic character into atom-based dispersion energy schemes. (arXiv:2308.11855v1 [cond-mat.mes-hall])
John F. Dobson, Alberto Ambroselli

The dispersion component of the van der Waals (vdW) interaction in low-dimensional metals is known to exhibit anomalous "Type-C non-additivity" [Int. J. Quantum Chem. 114, 1157 (2014)]. This causes dispersion energy behavior, at asymptotically large separations, that is missed by popular atom-based schemes for dispersion energy calculations. For example, the dispersion interaction energy between parallel metallic nanotubes at separation $D$ falls off aymptotically as approximately $D^{-2}$, whereas current atom-based schemes predict $D^{-5}$ asymptotically. To date it has not been clear whether current atom-based theories also give the dispersion interaction inaccurately at smaller separations for low-dimensional metals.

Here we introduce a new theory that we term "MBD+C" . It permits inclusion of Type C effects efficiently within atom-based dispersion energy schemes such as Many Body Dispersion (MBD) and Universal MBD (uMBD). This allows us to investigate asymptotic, intermediate and near-contact regimes with equal accuracy. (The large contact energy of intimate metallic bonding is not primarily governed by dispersion energy and is described well by semi-local density functional theory.) Here we apply a simplified version,"nn-MBD+C", of our new theory to calculate the dispersion interaction for three low-dimensional metallic systems: parallel metallic chains of gold atoms, parallel Li-doped graphene sheets; and parallel (4,4) armchair carbon nanotubes. In addition to giving the correct asymptotic behavior, the new theory seamlessly gives the dispersion energy down to near-contact geometry, where it is similar to MBD but can give up to 15% more dispersion energy than current MBD schemes, in the systems studied so far. This percentage increases with separation until nn-MBD+C dominates MBD at asymptotic separations.

Native Pb vacancy defects induced p-type characteristic in epitaxial monolayer PbSe. (arXiv:2308.11931v1 [cond-mat.mtrl-sci])
Qiwei Tian, Ping Li, Li Zhang, Yuan Tian, Long-Jing Yin, Lijie Zhang, Zhihui Qin

PbSe, a predicted two-dimensional (2D) topological crystalline insulator (TCI) in the monolayer limit, possess excellent thermoelectric and infrared optical properties. Native defects in PbSe take a crucial role for the applications. However, little attention has been paid to the defect induced doping characteristics. Here, we provide an experimental and theoretical investigation of defects induced p-type characteristic on epitaxial monolayer PbSe on Au(111). Scanning tunneling microscopy (STM) measurements demonstrate an epitaxial PbSe monolayer with a fourfold symmetric lattice. Combined scanning tunneling spectroscopy (STS) and density functional theory (DFT) calculations reveal a quasi-particle bandgap of 0.8eV of PbSe. STM results unveil that there are two types of defects on the surface, one is related the vacancies of Pb atoms and the other is the replacement of the absent Se atoms by Pb. Corresponding theoretical optimization confirms the structures of the defects. More importantly, both STS measurements and DFT calculations give evidence that the Pb vacancies move the Fermi energy inside the valence band and produce extra holes, leading to p-type characteristics of PbSe. Our work provides effective information for the future research of device performance based on PbSe films.

Detecting Strain Effects due to Nanobubbles in Graphene Mach-Zehnder Interferometers. (arXiv:2308.11954v1 [cond-mat.mes-hall])
Nojoon Myoung, Taegeun Song, Hee Chul Park

We investigate the effect of elastic strain on a Mach-Zehnder (MZ) interferometer created by graphene p-n junction in quantum Hall regime. We demonstrate that a Gaussian-shaped nanobubble causes detuning of the quantum Hall conductance oscillations across the p-n junction, due to the strain-induced local pseudo-magnetic fields. By performing a machine-learning-based Fourier analysis, we differentiate the nanobubble-induced Fourier component from the conductance oscillations originating from the external magnetic fields. We show that the detuning of the conductance oscillations is due to the altered pathway of quantum Hall interface channels caused by the strain-induced pseudo-magnetic fields. In the presence of the nanobubble, a new Fourier component for a magnetic flux $\Phi_{0}/2$ appears, and the corresponding MZ interferometry indicates that the enclosed area is reduced by half due to the strain-mediated pathway between two quantum Hall interface channels. Our findings suggest the potential of using graphene as a strain sensor for developments in graphene-based device fabrications and measurements technologies.

A study of Pt, Rh, Ni and Ir dispersion on anatase TiO2(101) and the role of water. (arXiv:2308.11973v1 [cond-mat.mtrl-sci])
Lena Puntscher, Kevin Daninger, Michael Schmid, Ulrike Diebold, Gareth S. Parkinson

Understanding how metal atoms are stabilized on metal oxide supports is important for predicting the stability of single-atom catalysts. In this study, we use scanning tunnelling microscopy (STM) and x-ray photoelectron spectroscopy (XPS) to investigate four catalytically active metals - Platinum, Rhodium, Nickel and Iridium - on the anatase TiO2(101) surface. The metals were vapor deposited at room temperature in ultrahigh vacuum (UHV) conditions, and also with a background water pressure of 2x10-8 mbar. Pt and Ni exist as a mixture of adatoms and nanoparticles in UHV at low coverage, with the adatoms immobilized at defect sites. Water has no discernible effect on the Pt dispersion, but significantly increases the amount of Ni single atoms. Ir is highly dispersed, but sinters to nanoparticles in the water vapor background leading to the formation of large clusters at step edges. Rh forms clusters on the terrace of anatase TiO2(101) irrespective of the environment. We conclude that introducing defect sites into metal oxide supports could be a strategy to aid the dispersion of single atoms on metal-oxide surfaces, and that the presence of water should be taken into account in the modelling of single-atom catalysts.

Irreducible momentum-space spin structure of Weyl semimetals and its signatures in Friedel oscillations. (arXiv:2308.11986v1 [cond-mat.mes-hall])
Andy Knoll, Carsten Timm

Materials that break time-reversal or inversion symmetry possess nondegenerate electronic bands, which can touch at so-called Weyl points. The spinor eigenstates in the vicinity of a Weyl point exhibit a well-defined chirality $\pm 1$. Numerous works have studied the consequences of this chirality, for example in unconventional magnetoelectric transport. However, even a Weyl point with isotropic dispersion is not only characterized by its chirality but also by the momentum dependence of the spinor eigenstates. For a single Weyl point, this momentum-space spin structure can be brought into standard "hedgehog" form by a unitary transformation, but for two or more Weyl points, this is not possible. In this work, we show that the relative spin structure of a pair of Weyl points has strong qualitative signatures in the electromagnetic response. Specifically, we investigate the Friedel oscillations in the induced charge density due to a test charge for a centrosymmetric system consisting of two Weyl points with isotropic dispersion. The most pronounced signature is that the amplitude of the Friedel oscillations falls off as $1/r^4$ in directions in which both Weyl points exhibit the same spin structure, while for directions with inverted spin structures, the amplitude of the Friedel oscillations decreases as $1/r^3$.

Parity-protected superconducting qubit based on topological insulators. (arXiv:2308.12027v1 [cond-mat.mes-hall])
Guo-Liang Guo, Han-Bing Leng, Xin Liu

We propose a novel architecture that utilizes two 0-$\pi$ qubits based on topological Josephson junctions to implement a parity-protected superconducting qubit. The topological Josephson junctions provides protection against fabrication variations, which ensures the identical Josephson junctions required to implement the0-$\pi$ qubit. By viewing the even and odd parity ground states of a 0-$\pi$ qubit as spin-$\frac{1}{2}$ states, we construct the logic qubit states using the total parity odd subspace of two 0-$\pi$ qubits. This parity-protected qubit exhibits robustness against charge noise, similar to a singlet-triplet qubit's immunity to global magnetic field fluctuations. Meanwhile, the flux noise cannot directly couple two states with the same total parity and therefore is greatly suppressed. Benefiting from the simultaneous protection from both charge and flux noise, we demonstrate a dramatic enhancement of both $T_1$ and $T_2$ coherence times. Our work presents a new approach to engineer symmetry-protected superconducting qubits.

Tailoring magnetism of nanographenes via tip-controlled dehydrogenation. (arXiv:2308.12036v1 [cond-mat.mtrl-sci])
Chenxiao Zhao, Qiang Huang, Leoš Valenta, Kristjan Eimre, Lin Yang, Aliaksandr V. Yakutovich, Wangwei Xu, Ji Ma, Xinliang Feng, Michal Jurí{č}ek, Roman Fasel, Pascal Ruffieux, Carlo A. Pignedoli

Atomically precise graphene nanoflakes, called nanographenes, have emerged as a promising platform to realize carbon magnetism. Their ground state spin configuration can be anticipated by Ovchinnikov-Lieb rules based on the mismatch of {\pi}-electrons from two sublattices. While rational geometrical design achieves specific spin configurations, further direct control over the {\pi}-electrons offers a desirable extension for efficient spin manipulations and potential quantum device operations. To this end, we apply a site-specific dehydrogenation using a scanning tunneling microscope tip to nanographenes deposited on a Au(111) substrate, which shows the capability of precisely tailoring the underlying {\pi}-electron system and therefore efficiently manipulating their magnetism. Through first-principles calculations and tight-binding mean-field-Hubbard modelling, we demonstrate that the dehydrogenation-induced Au-C bond formation along with the resulting hybridization between frontier {\pi}-orbitals and Au substrate states effectively eliminate the unpaired {\pi}-electron. Our results establish an efficient technique for controlling the magnetism of nanographenes.

A higher-order topological twist on cold-atom SO(5) Dirac fields. (arXiv:2308.12051v1 [cond-mat.quant-gas])
A. Bermudez, D. González-Cuadra, S. Hands

Ultracold Fermi gases of spin-3/2 atoms provide a clean platform to realise SO(5) models of 4-Fermi interactions in the laboratory. By confining the atoms in a two-dimensional Raman lattice, we show how this system can be used as a flexible quantum simulator of Dirac quantum field theories (QFTs) that combine Gross-Neveu and Thirring interactions with a higher-order topological twist. We show that the lattice model corresponds to a regularization of this QFT with an anisotropic twisted Wilson mass. This allows us to access higher-order topological states protected by a hidden SO(5) symmetry, a remnant of the original rotational symmetry of the 4-Fermi interactions that is not explicitly broken by the lattice discretization. Using large-$N$ methods, we show that the 4-Fermi interactions lead to a rich phase diagram with various competing fermion condensates. Our work opens a route for the implementation of correlated higher-order topological states with tunable interactions that has interesting connections to non-trivial relativistic QFTs of Dirac fermions in $D = 2 + 1$ dimensions.

Manipulation of magnetization and spin transport in hydrogenated graphene with THz pulses. (arXiv:2308.12076v1 [cond-mat.mes-hall])
Jakob Kjærulff Svaneborg, Aleksander Bach Lorentzen, Fei Gao, Antti-Pekka Jauho, Mads Brandbyge

Terahertz (THz) field pulses can now be applied in Scanning Tunnelling Microscopy (THz-STM) junction experiments to study time resolved dynamics. The relatively slow pulse compared to the typical electronic time-scale calls for approximations based on a time-scale separation. Here, we contrast three methods based on non-equilibrium Green's functions (NEGF): (i) the steady-state, adiabatic results, (ii) the lowest order dynamic expansion in the time-variation (DE), and (iii) the auxiliary mode (AM) propagation method without approximations in the time-variation. We consider a concrete THz-STM junction setup involving a hydrogen adsorbate on graphene where the localized spin polarization can be manipulated on/off by a local field from the tip electrode and/or a back-gate affecting the in-plane transport. We use steady-state NEGF combined with Density Functional Theory (DFT-NEGF) to obtain a Hubbard model for the study of the junction dynamics. Solving the Hubbard model in a mean-field approximation, we find that the near-adiabatic first order dynamical expansion provides a good description for STM voltage pulses up to the 1 V range.

Fractional quantum Hall edge polaritons. (arXiv:2308.12146v1 [cond-mat.mes-hall])
Lucas Winter, Oded Zilberberg

It is commonly believed that light cannot couple to the collective excitations of the fractional quantum Hall effect (FQHE). This assumption relies on Kohn's theorem that states that electron-electron interactions decouple from homogeneous electromagnetic fields due to galilean invariance. Here, we demonstrate that the existence of an edge breaks Kohn's theorem, and enables coupling of cavity light to the plasmonic edge modes of the FQHE. We derive the coupling using the FQHE bulk-boundary correspondence and predict the formation of experimentally detectable plasmon polaritons. We find that a single cavity mode leaves the system's topological protection intact. Interestingly, however, a multimode cavity mediates plasmon backscattering, and effectively transforms the edges of the 2D FQHE into a 1D wire. Such cavity-meditated nonlocal backscattering bodes the breakdown of the topological protection in the regime of ultra-strong photon-plasmon coupling. Our analytical framework and photoelectric findings pave the way for investigating the topological order of the FQHE via optical spectroscopic probes and provide new opportunities to control FQHE edge excitations using light.

Quantum bath augmented stochastic nonequilibrium atomistic simulations for molecular heat conduction. (arXiv:2308.12282v1 [cond-mat.mtrl-sci])
Renai Chen, Mohammadhasan Dinpajooh, Abraham Nitzan

Classical molecular dynamics (MD) has been shown to be effective in simulating heat conduction in certain molecular junctions since it inherently takes into account some essential methodological components which are lacking with quantum Landauer-type transport model, such as many-body full force-field interactions, anharmonicity effects and nonlinear responses for large temperature biases. However, the classical mechanics reaches its limit in the environments where the quantum effects are significant (e.g. with low-temperatures substrates, presence of extremely high frequency molecular modes). Here, we present an atomistic simulation methodology for molecular heat conduction that incorporates the quantum Bose-Einstein statistics into an effective temperature in the form of modified Langevin equation. We show that the results from such a quasi-classical effective temperature (QCET) MD method deviates drastically when the baths temperature approaches zero from classical MD simulations and the results converge to the classical ones when the bath approaches the high-temperature limit, which makes the method suitable for full temperature range. In addition, we show that our quasi-classical thermal transport method can be used to model the conducting substrate layout and molecular composition (e.g. anharmonicities, high-frequency modes). Anharmonic models are explicitly simulated via the Morse potential and compared to pure harmonic interactions, to show the effects of anharmonicities under quantum colored bath setups. Finally, the chain length dependence of heat conduction is examined for one-dimensional polymer chains placed in between quantum augmented baths.

Correlated Zak insulator in organic antiferromagnets. (arXiv:2301.04490v2 [cond-mat.str-el] UPDATED)
Takahiro Misawa, Makoto Naka

Searching for topological insulators in solids is one of the main issues of modern condensed matter physics since robust gapless edge or surface states of the topological insulators can be used as building blocks of next-generation devices. Enhancing spin-orbit couplings is a promising way to realize topological insulators in solids, whereas the amplitude of the spin-orbit couplings is not sufficiently large in most materials. Here we show a way to realize a topological state characterized by the quantized Zak phase, termed the Zak insulator, with spin-polarized edges in organic antiferromagnetic Mott insulators without relying on the spin-orbit coupling. The obtained Zak insulator can have a large charge gap compared to the conventional topological insulators, since Coulomb interactions mainly govern the amplitude of the charge gap in the antiferromagnetic Mott insulators. Besides the mean-field analysis, we demonstrate that the Zak insulator survives against electron correlation effects by calculating the many-body Zak phase. Our finding provides an unprecedented way to realize a topological state in strongly correlated electron systems.

Dirac signal processing of higher-order topological signals. (arXiv:2301.10137v2 [eess.SP] UPDATED)
Lucille Calmon, Michael T. Schaub, Ginestra Bianconi

Higher-order networks can sustain topological signals which are variables associated not only to the nodes, but also to the links, to the triangles and in general to the higher dimensional simplices of simplicial complexes. These topological signals can describe a large variety of real systems including currents in the ocean, synaptic currents between neurons and biological transportation networks. In real scenarios topological signal data might be noisy and an important task is to process these signals by improving their signal to noise ratio. So far topological signals are typically processed independently of each other. For instance, node signals are processed independently of link signals, and algorithms that can enforce a consistent processing of topological signals across different dimensions are largely lacking. Here we propose Dirac signal processing, an adaptive, unsupervised signal processing algorithm that learns to jointly filter topological signals supported on nodes, links and triangles of simplicial complexes in a consistent way. The proposed Dirac signal processing algorithm is formulated in terms of the discrete Dirac operator which can be interpreted as "square root" of a higher-order Hodge Laplacian. We discuss in detail the properties of the Dirac operator including its spectrum and the chirality of its eigenvectors and we adopt this operator to formulate Dirac signal processing that can filter noisy signals defined on nodes, links and triangles of simplicial complexes. We test our algorithms on noisy synthetic data and noisy data of drifters in the ocean and find that the algorithm can learn to efficiently reconstruct the true signals outperforming algorithms based exclusively on the Hodge Laplacian.

Tetrahedral triple-Q magnetic ordering and large spontaneous Hall conductivity in the metallic triangular antiferromagnet Co1/3TaS2. (arXiv:2303.03760v4 [cond-mat.str-el] UPDATED)
Pyeongjae Park, Woonghee Cho, Chaebin Kim, Yeochan An, Yoon-Gu Kang, Maxim Avdeev, Romain Sibille, Kazuki Iida, Ryoichi Kajimoto, Ki Hoon Lee, Woori Ju, En-Jin Cho, Han-Jin Noh, Myung Joon Han, Shang-Shun Zhang, Cristian D. Batista, Je-Geun Park

The triangular lattice antiferromagnet (TLAF) has been the standard paradigm of frustrated magnetism for several decades. The most common magnetic ordering in insulating TLAFs is the 120 structure. However, a new triple-Q chiral ordering can emerge in metallic TLAFs, representing the short wavelength limit of magnetic skyrmion crystals. We report the metallic TLAF Co1/3TaS2 as the first example of tetrahedral triple-Q ordering with the associated topological Hall effect (non-zero {\sigma}xy(H=0)). Our measurements of the inelastic neutron scattering cross section are also consistent with the calculated dynamical structure factor of the tetrahedral triple-Q state.

Higher-order topological and nodal superconducting transition-metal sulfides MS (M = Nb and Ta). (arXiv:2304.03062v3 [cond-mat.supr-con] UPDATED)
Yipeng An, Juncai Chen, Yong Yan, Jinfeng Wang, Yinong Zhou, Zhengxuan Wang, Chunlan Ma, Tianxing Wang, Ruqian Wu, Wuming Liu

Intrinsic topological superconducting materials are exotic and vital to develop the next-generation topological superconducting devices, topological quantum calculations, and quantum information technologies. Here, we predict the topological and nodal superconductivity of MS (M = Nb and Ta) transition-metal sulfides by using the density functional theory for superconductors combining with the symmetry indicators. We reveal their higher-order topology nature with an index of Z4 = 2. These materials have a higher Tc than the Nb or Ta metal superconductors due to their flat-band and strong electron-phonon coupling nature. Electron doping and lighter isotopes can effectively enhance the Tc. Our findings show that the MS (M = Nb and Ta) systems can be new platforms to study exotic physics in the higher-order topological superconductors, and provide a theoretical support to utilize them as the topological superconducting devices in the field of advanced topological quantum calculations and information technologies.

Chemically detaching hBN crystals grown at atmospheric pressure and high temperature for high-performance graphene devices. (arXiv:2304.03149v2 [cond-mat.mes-hall] UPDATED)
Taoufiq Ouaj, Leonard Kramme, Marvin Metzelaars, Jiahan Li, Kenji Watanabe, Takashi Taniguchi, James H. Edgar, Bernd Beschoten, Paul Kögerler, Christoph Stampfer

In this work, we report on the growth of hexagonal boron nitride (hBN) crystals from an iron flux at atmospheric pressure and high temperature and demonstrate that (i) the entire sheet of hBN crystals can be detached from the metal in a single step using hydrochloric acid and that (ii) these hBN crystals allow the fabrication of high carrier mobility graphene devices. By combining spatially-resolved confocal Raman spectroscopy and electrical transport measurements, we confirm the excellent quality of these crystals for high-performance hBN-graphene-based van der Waals heterostructures. The full width at half maximum of the graphene Raman 2D peak is as low as 16 cm$^{-1}$, and the room temperature charge carrier mobilitiy is around 80000 cm$^2$/(Vs) at a carrier density 1$\times$10$^{12}$cm$^{-12}$. This is fully comparable with devices of similar dimensions fabricated using crystalline hBN synthesized by the high pressure and high temperature method. Finally, we show that for exfoliated high-quality hBN flakes with a thickness between 20 nm and 40 nm the line width of the hBN Raman peak, in contrast to the graphene 2D line width, is not useful for benchmarking hBN in high mobility graphene devices.

Bulk-edge correspondence of Stiefel-Whitney and Euler insulators through the entanglement spectrum and cutting procedure. (arXiv:2304.06974v2 [cond-mat.mes-hall] UPDATED)
Ryo Takahashi, Tomoki Ozawa

We propose an unconventional bulk-edge correspondence for two-dimensional Stiefel-Whitney insulators and Euler insulators, which are topological insulators protected by the $PT$ symmetry. We find that, although the energy spectrum under the open boundary condition is generally gapped, the entanglement spectrum is gapless when the Stiefel-Whitney or Euler class is nonzero. The robustness of the gapless spectrum for Stiefel-Whitney insulator can be understood through an emergent anti-unitary particle-hole symmetry. For the Euler insulators, we propose a conjecture, which is supported by our numerical calculation, that the Euler class is equal to the number of crossing in the entanglement spectrum, taking into account the degree of the crossings. We also discuss that these crossings of the entanglement spectrum are related to the gap closing points in the cutting procedure, which is the energy spectrum as the magnitude of the boundary hopping is varied.

Fractional quantum anomalous Hall states in twisted bilayer MoTe$_2$ and WSe$_2$. (arXiv:2304.12261v3 [cond-mat.mes-hall] UPDATED)
Aidan P. Reddy, Faisal F. Alsallom, Yang Zhang, Trithep Devakul, Liang Fu

We demonstrate via exact diagonalization that AA-stacked TMD homobilayers host fractional quantum anomalous Hall (FQAH) states with fractionally quantized Hall conductance at fractional fillings $n=\frac{1}{3},\, \frac{2}{3}$ and zero magnetic field. While both states are most robust at angles near $\theta\approx 2^{\circ}$, the $n=\frac{1}{3}$ state gives way to a charge density wave with increasing twist angle whereas the $n=\frac{2}{3}$ state survives across a much broader range of twist angles. We show that the competition between FQAH states and charge density wave or metallic phases is primarily controlled by the wavefunctions and dispersion of the underlying Chern band, respectively. Additionally, Ising ferromagnetism is found across a broad range of fillings where the system is insulating or metallic alike. The spin gap is enhanced at filling fractions where integer and fractional quantum anomalous Hall states are formed.

Voltage-tunable giant nonvolatile multiple-state resistance in sliding-interlayer ferroelectric h-BN van der Waals multiferroic tunnel junction. (arXiv:2305.06126v2 [cond-mat.mes-hall] UPDATED)
Xinlong Dong, Xuemin Shen, Xiaowen Sun, Yuhao Bai, Zhi Yan, Xiaohong Xu

Multiferroic tunnel junctions (MFTJs) based on two-dimensional (2D) van der Waals heterostructures with sharp and clean interfaces at the atomic scale are crucial for applications in nanoscale multi-resistive logic memory devices. The recently discovered sliding ferroelectricity in 2D van der Waals materials has opened new avenues for ferroelectric-based devices. Here, we theoretically investigate the spin-dependent electronic transport properties of Fe$_3$GeTe$_2$/graphene/bilayer-$h$-BN/graphene/CrI$_3$ (FGT/Gr-BBN-Gr/CrI) all-vdW MFTJs by employing the nonequilibrium Green's function combined with density functional theory. We demonstrate that such FGT/Gr-BBN-Gr/CrI MFTJs exhibit four non-volatile resistance states associated with different staking orders of sliding ferroelectric BBN and magnetization alignment of ferromagnetic free layer CrI$_3$, with a maximum tunnel magnetoresistance (electroresistance) ratio, i.e., TMR (TER) up to $\sim$$3.36\times10^{4}$\% ($\sim$$6.68\times10^{3}$\%) at a specific bias voltage. Furthermore, the perfect spin filtering and remarkable negative differential resistance effects are evident in our MFTJs. We further discover that the TMR, TER, and spin polarization ratio under an equilibrium state can be enhanced by the application of in-plane biaxial strain. This work shows that the giant tunneling resistance ratio, multiple resistance states, and excellent spin-polarized transport properties of sliding ferroelectric BBN-based MFTJs indicate its significant potential in nonvolatile memories.

Mixed-State Quantum Spin Liquids and Dynamical Anyon Condensations in Kitaev Lindbladians. (arXiv:2305.09197v3 [cond-mat.str-el] UPDATED)
Kyusung Hwang

Quantum spin liquids and anyons, used to be subjects of condensed matter physics, now are realized in various platforms of qubits, offering unprecedented opportunities to investigate fundamental physics of many-body quantum entangled states. Qubits are inevitably exposed to environment effects such as decoherence and dissipation, which are believed to be detrimental to many-body entanglement. Here, we argue that unlike the common belief decoherence and dissipation can give rise to novel topological phenomena in quantum spin liquids. We study open quantum systems of the Kitaev spin liquid and the toric code via the Lindblad master equation approach. By using exact solutions and numerical approaches, we show the dynamical occurrence of anyon condensation by decoherence and dissipation, which results in a topological transition from the initial state spin liquid to the steady state spin liquid. The mechanism of the anyon condensation transition by the Lindblad dynamics is elucidated. We also provide an insight into the relationship between the Kitaev spin liquid and the toric code in the picture of anyon condensation. Our work suggests open quantum systems to be a new venue for topological phenomena of quantum spin liquids and anyons.

Ab-initio overestimation of the topological region in Eu-based compounds. (arXiv:2305.10804v2 [cond-mat.str-el] UPDATED)
Giuseppe Cuono, Raghottam M. Sattigeri, Carmine Autieri, Tomasz Dietl

An underestimation of the fundamental band gap values by the density functional theory within the local density approximation and associated approaches is a well-known challenge of ab-initio electronic structure computations. Motivated by recent optical experiments [D. Santos-Cottin et al., arXiv:2301.08014], we have revisited first-principle results obtained earlier for EuCd2As2 and extended the computational studies to the whole class of systems EuCd2X2 (X = P, As, Sb, Bi), to EuIn2X2 (X = P, As, Sb), and to nonmagnetic AEIn2As2 (AE= Ca, Sr, Ba) employing a hybrid functional method. We find that our approach provides the magnitude of the energy gap for EuCd2As2 in agreement with the experimental value. Actually, our results indicate that EuSn2As2, BaIn2As2, EuCd2Bi2 and EuCd2SbBi are robust topological insulators, while all other compounds are topologically trivial semiconductors. The trivial band gaps of EuCd2P2, EuCd2As2 and EuCd2Sb2 are in the range of 1.38-1.48 eV, 0.72-0.79 eV and 0.46-0.49 eV, respectively. The topologically trivial Eu-based systems are antiferromagnetic semiconductors with a strong red shift of the energy gap in a magnetic field caused by the exchange coupling of the band states to spins localized on the 4f-shell of Eu ions. Additionally, the EuIn2X2 (X = P, As) compounds show altermagnetic exchange-induced band spin-splitting, particularly noticeable in the case of states derived from 5d-Eu orbitals.

Spectroscopic evidence for topological band structure in FeTe$_{0.55}$Se$_{0.45}$. (arXiv:2307.03861v2 [cond-mat.str-el] UPDATED)
Y.-F. Li, S.-D. Chen, M. Garcia-Diez, M. I. Iraola, H. Pfau, Y.-L. Zhu, Z.-Q. Mao, T. Chen, M. Yi, P.-C. Dai, J.A. Sobota, M. Hashimoto, M. G. Vergniory, D.-H. Lu, Z.-X. Shen

FeTe$_{0.55}$Se$_{0.45}$(FTS) occupies a special spot in modern condensed matter physics at the intersections of electron correlation, topology, and unconventional superconductivity. The bulk electronic structure of FTS is predicted to be topologically nontrivial thanks to the band inversion between the $d_{xz}$ and $p_z$ bands along $\Gamma$-$Z$. However, there remain debates in both the authenticity of the Dirac surface states (DSS) and the experimental deviations of band structure from the theoretical band inversion picture. Here we resolve these debates through a comprehensive ARPES investigation. We first observe a persistent DSS independent of $k_z$. Then, by comparing FTS with FeSe which has no band inversion along $\Gamma$-$Z$, we identify the spectral weight fingerprint of both the presence of the $p_z$ band and the inversion between the $d_{xz}$ and $p_z$ bands. Furthermore, we propose a reconciling band structure under the framework of a tight-binding model preserving crystal symmetry. Our results highlight the significant influence of correlation on modifying the band structure and make a strong case for the existence of topological band structure in this unconventional superconductor.

Single crystal synthesis, structure, and magnetism of Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O. (arXiv:2308.06256v2 [cond-mat.supr-con] UPDATED)
P. Puphal, M. Y. P. Akbar, M. Hepting, E. Goering, M. Isobe, A. A. Nugroho, B. Keimer

The recent claim of superconductivity above room temperature in Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O with 0.9 < $x$ < 1 (referred to as LK-99) has sparked considerable interest. To minimize the influence of structural defects and impurity phases on the physical properties, we have synthesized phase-pure single crystals with $x \sim 1$. We find that the crystals are highly insulating and optically transparent. X-ray analysis reveals an uneven distribution of the substituted Cu throughout the sample. Temperature ($T$) dependent magnetization measurements for $ 2 \leq T \leq 800$ K reveal the diamagnetic response characteristic of a non-magnetic insulator, as well as a small ferromagnetic component, possibly originating from frustrated exchange interactions in Cu-rich clusters in the Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O structure. No anomalies indicative of phase transitions are observed. We therefore rule out the presence of superconductivity in Pb$_{9}$Cu(PO$_4$)$_6$O crystals, and provide some considerations on the origin of anomalies previously reported in experiments on polycrystalline specimen.

Found 3 papers in prb
Date of feed: Thu, 24 Aug 2023 03:16:58 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]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Josephson diode effect in a line-centered honeycomb lattice based superconductor junction
Ya-Jun Wei, Juan-Juan Wang, and J. Wang
Author(s): Ya-Jun Wei, Juan-Juan Wang, and J. Wang

The Josephson diode effect (JDE) is the asymmetry of the critical supercurrent flowing along opposite current directions. We study a mechanism in this work to generate a possible JDE in the two-dimensional line-centered honeycomb (LCH) lattice based Josephson junction in which the supercurrent flows…

[Phys. Rev. B 108, 054521] Published Wed Aug 23, 2023

Orbital Hall physics in two-dimensional Dirac materials
Armando Pezo, Diego García Ovalle, and Aurélien Manchon
Author(s): Armando Pezo, Diego García Ovalle, and Aurélien Manchon

Orbitronics has recently emerged as a very active research topic after several proposals aiming to exploit the orbital degree of freedom for charge-free electronics. In this communication, we investigate orbital transport in selected two-dimensional systems to better understand which parameters gove…

[Phys. Rev. B 108, 075427] Published Wed Aug 23, 2023

Electron-electron interaction and correlation-induced two density waves with different Fermi velocities in graphene quantum dots
Hui-Ying Ren, Ya-Ning Ren, Qi Zheng, Jia-Qi He, and Lin He
Author(s): Hui-Ying Ren, Ya-Ning Ren, Qi Zheng, Jia-Qi He, and Lin He

Graphene quantum dots (GQDs) can exhibit a range of spectacular phenomena such as the Klein tunneling induced quasibound states and Berry phase tuned energy spectra. According to previous studies, all these interesting quantum phenomena seem to be well understood in the free electron picture. Howeve…

[Phys. Rev. B 108, L081408] Published Wed Aug 23, 2023

Found 1 papers in prl
Date of feed: Thu, 24 Aug 2023 03:16:59 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]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Toward a Unified Description of Isoscalar Giant Monopole Resonances in a Self-Consistent Quasiparticle-Vibration Coupling Approach
Z. Z. Li (李征征), Y. F. Niu (牛一斐), and G. Colò
Author(s): Z. Z. Li (李征征), Y. F. Niu (牛一斐), and G. Colò

The nuclear incompressibility is a key parameter of the nuclear equation of state that can be extracted from the measurements of the so-called “breathing mode” of finite nuclei. The most serious discrepancy so far is between values extracted from Pb and Sn, that has provoked the longstanding questio…

[Phys. Rev. Lett. 131, 082501] Published Wed Aug 23, 2023

Found 7 papers in nano-lett
Date of feed: Wed, 23 Aug 2023 13:05:16 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]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

[ASAP] Photoinduced Nonvolatile Resistive Switching Behavior in Oxygen-Doped MoS2 for a Neuromorphic Vision System
Ke Chang, Xinhui Zhao, Xinna Yu, Zhikai Gan, Renzhi Wang, Anhua Dong, Zhuyikang Zhao, Yafei Zhang, and Hui Wang

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Nano Letters
DOI: 10.1021/acs.nanolett.3c02499

[ASAP] Coherent Phonons in van der Waals MoSe2/WSe2 Heterobilayers
Changxiu Li, Alexey V. Scherbakov, Pedro Soubelet, Anton K. Samusev, Claudia Ruppert, Nilanthy Balakrishnan, Vitalyi E. Gusev, Andreas V. Stier, Jonathan J. Finley, Manfred Bayer, and Andrey V. Akimov

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Nano Letters
DOI: 10.1021/acs.nanolett.3c02316

[ASAP] Uncooled Mid-Infrared Sensing Enabled by Chip-Integrated Low-Temperature-Grown 2D PdTe2 Dirac Semimetal
Longhui Zeng, Wei Han, Xiaoyan Ren, Xue Li, Di Wu, Shujuan Liu, Hao Wang, Shu Ping Lau, Yuen Hong Tsang, Chong-Xin Shan, and Jiansheng Jie

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Nano Letters
DOI: 10.1021/acs.nanolett.3c02396

[ASAP] Switching the Moiré Lattice Models in the Twisted Bilayer WSe2 by Strain or Pressure
Yifan Gao, Qiaoling Xu, M. Umar Farooq, Lede Xian, and Li Huang

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Nano Letters
DOI: 10.1021/acs.nanolett.3c01756

[ASAP] Trapping Hydrogen Molecules between Perfect Graphene
Jie Xu, Weilin Liu, Wenna Tang, Gan Liu, Yujian Zhu, Guowen Yuan, Lei Wang, Xiaoxiang Xi, and Libo Gao

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Nano Letters
DOI: 10.1021/acs.nanolett.3c02321

[ASAP] Elastocaloric Effect in Graphene Kirigami
Luiz A. Ribeiro Junior, Marcelo L. Pereira Junior, and Alexandre F. Fonseca

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Nano Letters
DOI: 10.1021/acs.nanolett.3c02260

[ASAP] Spatially Coherent Tip-Enhanced Raman Spectroscopy Measurements of Electron–Phonon Interaction in a Graphene Device
Rafael Battistella Nadas, Andreij C. Gadelha, Tiago C. Barbosa, Cassiano Rabelo, Thiago de Lourenço e Vasconcelos, Vitor Monken, Ary V. R. Portes, Kenji Watanabe, Takashi Taniguchi, Jhonattan C. Ramirez, Leonardo C. Campos, Riichiro Saito, Luiz Gustavo Cançado, and Ado Jorio

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Nano Letters
DOI: 10.1021/acs.nanolett.3c00851

Found 6 papers in acs-nano
Date of feed: Wed, 23 Aug 2023 13:02:49 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]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

[ASAP] Electroluminescence from Megasonically Solution-Processed MoS2 Nanosheet Films
Sonal V. Rangnekar, Vinod K. Sangwan, Mengru Jin, Maryam Khalaj, Beata M. Szydłowska, Anushka Dasgupta, Lidia Kuo, Heather E. Kurtz, Tobin J. Marks, and Mark C. Hersam

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ACS Nano
DOI: 10.1021/acsnano.3c06034

[ASAP] Electrochemical Li+ Insertion/Extraction Reactions at LiPON/Epitaxial Graphene Interfaces
Satoshi Yamamoto, Munekazu Motoyama, Masahiko Suzuki, Ryotaro Sakakibara, Norikazu Ishigaki, Akichika Kumatani, Wataru Norimatsu, and Yasutoshi Iriyama

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ACS Nano
DOI: 10.1021/acsnano.3c00158

[ASAP] Sub-5 nm Contacts and Induced p–n Junction Formation in Individual Atomically Precise Graphene Nanoribbons
Pin-Chiao Huang, Hongye Sun, Mamun Sarker, Christopher M. Caroff, Gregory S. Girolami, Alexander Sinitskii, and Joseph W. Lyding

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ACS Nano
DOI: 10.1021/acsnano.3c02794

[ASAP] Ultrafast Electronic Relaxation Dynamics of Atomically Thin MoS2 Is Accelerated by Wrinkling
Ce Xu, Guoqing Zhou, Evgeny M. Alexeev, Alisson R. Cadore, Ioannis Paradisanos, Anna K. Ott, Giancarlo Soavi, Sefaattin Tongay, Giulio Cerullo, Andrea C. Ferrari, Oleg V. Prezhdo, and Zhi-Heng Loh

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ACS Nano
DOI: 10.1021/acsnano.3c02917

[ASAP] Edge Contacts to Atomically Precise Graphene Nanoribbons
Wenhao Huang, Oliver Braun, David I. Indolese, Gabriela Borin Barin, Guido Gandus, Michael Stiefel, Antonis Olziersky, Klaus Müllen, Mathieu Luisier, Daniele Passerone, Pascal Ruffieux, Christian Schönenberger, Kenji Watanabe, Takashi Taniguchi, Roman Fasel, Jian Zhang, Michel Calame, and Mickael L. Perrin

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ACS Nano
DOI: 10.1021/acsnano.3c00782

[ASAP] Ultra-Wideband Mid-Infrared Chalcogenide Suspended Nanorib Waveguide Gas Sensors with Exceptionally High External Confinement Factor beyond Free-Space
Mingquan Pi, Chuantao Zheng, Huan Zhao, Zihang Peng, Gangyun Guan, Jialin Ji, Yijun Huang, Yuting Min, Lei Liang, Fang Song, Xue Bai, Yu Zhang, Yiding Wang, and Frank K. Tittel

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ACS Nano
DOI: 10.1021/acsnano.3c02699