Found 36 papers in cond-mat
Date of feed: Thu, 23 Nov 2023 01:30:00 GMT

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Edge-pinning effect of graphene nanoflakes sliding atop graphene. (arXiv:2311.12853v1 [cond-mat.mtrl-sci])
Yingchao Liu, Jinlong Ren, Decheng Kong, Guangcun Shan, Kunpeng Dou

Edge effect is one of the detrimental factors preventing superlubricity in laminar solid lubricants. Separating the friction contribution from the edge atom and inner atom is of paramount importance for rational design of ultralow friction across scales in van der Waals heterostructures. To decouple these contributions and provide the underlying microscopic origin at the atomistic level, we considered two contrast models, namely, graphene nanoflakes with dimerized and pristine edges sliding on graphene monolayer based on extensive ab initio calculations. We found the edge contribution to friction is lattice orientation dependence. In particular, edge pinning effect by dimerization is obvious for misaligned contact but suppressed in aligned lattice orientation. The former case providing local commensuration along edges is reminiscent of Aubry's pinned phase and the contribution of per edge carbon atom to the sliding potential energy corrugation is even 1.5 times more than that of an atom in bilayer graphene under commensurate contact. Furthermore, we demonstrated that the dimerized edges as high frictional pinning sites are robust to strain engineering and even enhanced by fluorination. Both structural and chemical modification in the tribological system constructed here offers the atomic details to dissect the undesirable edge pinning effect in layered materials which may give rise to the marked discrepancies in measured friction parameters from the same superlubric sample or different samples with the same size and identical preparation.

Moir\'e Fractional Chern Insulators II: First-principles Calculations and Continuum Models of Rhombohedral Graphene Superlattices. (arXiv:2311.12920v1 [cond-mat.mes-hall])
Jonah Herzog-Arbeitman, Yuzhi Wang, Jiaxuan Liu, Pok Man Tam, Ziyue Qi, Yujin Jia, Dmitri K. Efetov, Oskar Vafek, Nicolas Regnault, Hongming Weng, Quansheng Wu, B. Andrei Bernevig, Jiabin Yu

The experimental discovery of fractional Chern insulators (FCIs) in rhombohedral pentalayer graphene twisted on hexagonal boron nitride (hBN) has preceded theoretical prediction. Supported by large-scale first principles relaxation calculations at the experimental twist angle of $0.77^\circ$, we obtain an accurate continuum model of $n=3,4,5,6,7$ layer rhombohedral graphene-hBN moir\'e systems. Focusing on the pentalayer case, we analytically explain the robust $|C|=0,5$ Chern numbers seen in the low-energy single-particle bands and their flattening with displacement field, making use of a minimal two-flavor continuum Hamiltonian derived from the full model. We then predict nonzero valley Chern numbers at the $\nu = -4,0$ insulators observed in experiment. Our analysis makes clear the importance of displacement field and the moir\'e potential in producing localized "heavy fermion" charge density in the top valence band, in addition to the nearly free conduction band. Lastly, we study doubly aligned devices as additional platforms for moir\'e FCIs with higher Chern number bands.

Controlled expansion for transport in a class of non-Fermi liquids. (arXiv:2311.12922v1 [cond-mat.str-el])
Zhengyan Darius Shi

Non-Fermi liquids arise when strong interactions destroy stable fermionic quasiparticles. The simplest models featuring this phenomenon involve a Fermi surface coupled to fluctuating gapless bosonic order parameter fields, broadly referred to as "Hertz-Millis" models. We revisit a controlled approach to Hertz-Millis models that combines an expansion in the inverse number ($N$) of fermion species with an expansion in the deviation of the boson dynamical critical exponent $z$ from 2. The structure of the expansion is found to be qualitatively different in the quantum critical regime $\Omega \ll q$ and in the transport regime $\Omega \gg q$. In particular, correlation functions in the transport regime involve infinitely many diagrams at each order in perturbation theory. We provide an explicit and tractable recipe to classify and resum these diagrams. For the simplest Hertz-Millis models, we show that this recipe is consistent with non-perturbative anomaly arguments and correctly captures the fixed point optical conductivity as well as leading corrections from irrelevant operators. We comment on potential applications of this expansion to transport in more complicated Hertz-Millis models as well as certain beyond-Landau metallic quantum critical points.

Spectroscopy of a single-carrier bilayer graphene quantum dot from time-resolved charge detection. (arXiv:2311.12949v1 [cond-mat.mes-hall])
Hadrien Duprez, Solenn Cances, Andraz Omahen, Michele Masseroni, Max J. Ruckriegel, Christoph Adam, Chuyao Tong, Jonas Gerber, Rebekka Garreis, Wister Huang, Lisa Gächter, Takashi Taniguchi, Kenji Watanabe, Thomas Ihn, Klaus Ensslin

We measured the spectrum of a single-carrier bilayer graphene quantum dot as a function of both parallel and perpendicular magnetic fields, using a time-resolved charge detection technique that gives access to individual tunnel events. Thanks to our unprecedented energy resolution of 4$\mu~$eV, we could distinguish all four levels of the dot's first orbital, in particular in the range of magnetic fields where the first and second excited states cross ($B_\perp\lesssim 100~$mT). We thereby experimentally establish, the hitherto extrapolated, single-charge carrier spectrum picture and provide a new upper bound for the inter-valley mixing, equal to our energy resolution.

Mechanistic Insights into the Hydrazine-induced Chemical Reduction Pathway of Graphene Oxide. (arXiv:2311.13086v1 [cond-mat.dis-nn])
Shu Chen, Jianqiang Guo

Hydrazine stands out as the most generally used chemical-reducing agent for reducing graphene oxide. Despite numerous experimental and theoretical investigations into the reduction reaction, the reduction mechanism remains unclear. In this study, we propose that, in aqueous hydrazine solutions, both hydrazine and hydroxide ions could initiate the reduction of graphene oxide. We introduce a chemical reaction pathway involving C-H cleavage and a dehydroxylation process for the reduction of graphene oxide. By utilizing density functional theory calculations, the reduction reactions mediated by hydrazine and hydroxide ions are separately investigated. The reaction routes on the basal plane and edge regions of graphene oxide are discussed independently. The density functional theory calculations demonstrate that the proposed mechanism is both thermodynamically and dynamically feasible. This work might contribute to an atomic-level comprehension of a longstanding challenge in the field of graphene oxide.

Multiphoton-pumped UV-Vis transient absorption spectroscopy of 2D materials: basic concepts and recent applications. (arXiv:2311.13098v1 [cond-mat.mes-hall])
Yuri D Glinka

2D materials are considered a key element in the development of next-generation electronics (nanoelectronics) due to their extreme thickness in the nanometer range and unique physical properties. The ultrafast dynamics of photoexcited carriers in such materials is strongly influenced by their interfaces, since the thickness of 2D materials is much smaller than the typical depth of light penetration into them and the mean free path of photoexcited carriers. The resulting collisions of photoexcited carriers with interfacial potential barriers of 2D materials in the presence of a strong laser field significantly alter the overall dynamics of photoexcitation, allowing laser light to be directly absorbed by carriers in the conduction/valence band through the inverse bremsstrahlung mechanism. The corresponding ultrafast carrier dynamics can be monitored using multiphoton-pumped UV-Vis transient absorption spectroscopy. In this review, we discuss the basic concepts and recent applications of this spectroscopy for a variety of 2D materials, including transition-metal dichalcogenide monolayers, topological insulators, and other 2D semiconductor structures.

Magneto-structural phase transitions and two-dimensional spin waves in graphite. (arXiv:2311.13116v1 [cond-mat.supr-con])
Nadina Gheorghiu, Charles R. Ebbing, Timothy J. Haugan

We have previously found experimental evidence for several quantum phenomena in oxygen-ion implanted of hydrogenated graphite: ferromagnetism, antiferromagnetism, paramagentism, triplet superconductivity, Andreev states, Little-Parks oscillations, Lamb shift, Casimir effect, colossal magnetoresistance, and topologically-protected flat-energy bands [1-6]. Triplet superconductivity results in the formation of Josephson junctions, thus with potential of being used for spintronics applications in the critical area of quantum computing. In this paper, we are showing new experimental evidence for the formation of two-dimensional (2D) spin waves in oxygen-ion enriched and in hydrogenated highly oriented pyrolytic graphite. The temperature evolution of the remanent magnetization Mrem(T) data confirms the formation of spin waves that follow the 2D Heisenberg model with a weak uniaxial anisotropy. In addition, the step-like features also found in the temperature dependence of the electrical resistivity between insulating and metallic states suggest several outstanding possibilities, such as a structural transition, triplet superconductivity, and chiral properties.

Inducing a Tunable Skyrmion-Antiskyrmion System through Ion Beam Modification of FeGe Films. (arXiv:2311.13130v1 [cond-mat.mtrl-sci])
M. B. Venuti, Xiyue S. Zhang, Eric J Lang, Sadhvikas J. Addamane, Hanjong Paik, Portia Allen, Peter Sharma, David Muller, Khalid Hattar, Tzu-Ming Lu, Serena Eley

Skyrmions and antiskyrmions are nanoscale swirling textures of magnetic moments formed by chiral interactions between atomic spins in magnetic non-centrosymmetric materials and multilayer films with broken inversion symmetry. These quasiparticles are of interest for use as information carriers in next-generation, low-energy spintronic applications. To develop skyrmion-based memory and logic, we must understand skyrmion-defect interactions with two main goals -- determining how skyrmions navigate intrinsic material defects and determining how to engineer disorder for optimal device operation. Here, we introduce a tunable means of creating a skyrmion-antiskyrmion system by engineering the disorder landscape in FeGe using ion irradiation. Specifically, we irradiate epitaxial B20-phase FeGe films with 2.8 MeV Au$^{4+}$ ions at varying fluences, inducing amorphous regions within the crystalline matrix. Using low-temperature electrical transport and magnetization measurements, we observe a strong topological Hall effect with a double-peak feature that serves as a signature of skyrmions and antiskyrmions. These results are a step towards the development of information storage devices that use skyrmions and anitskyrmions as storage bits and our system may serve as a testbed for theoretically predicted phenomena in skyrmion-antiskyrmion crystals.

Bulk--boundary correspondence in a non-Hermitian quantum spin-Hall insulator. (arXiv:2311.13142v1 [cond-mat.mes-hall])
Chihiro Ishii, Yositake Takane

We focus on a scenario of non-Hermitian bulk--boundary correspondence that uses a topological invariant defined in a bulk geometry under a modified periodic boundary condition. Although this has succeeded in describing the topological nature of various one-dimensional non-Hermitian systems, its application to two-dimensional systems has been limited to a non-Hermitian Chern insulator. Here, we adapt the scenario to a non-Hermitian quantum spin-Hall insulator to extend its applicability. We show that it properly describes the bulk--boundary correspondence in the non-Hermitian quantum spin-Hall insulator. A phase diagram derived from the bulk--boundary correspondence is shown to be consistent with spectra of the system under an open boundary condition.

Fractional quantum Hall interface induced by geometric singularity. (arXiv:2311.13181v1 [cond-mat.mes-hall])
Qi Li, Yi Yang, Zhou Li, Hao Wang, Zi-Xiang Hu

The geometric response of quantum Hall liquids is an important aspect to understand their topological characteristics in addition to the electromagnetic response. According to the Wen-Zee theory, the topological spin is coupled to the curvature of the space in which the electrons reside. The presence of conical geometry provides a local isolated geometric singularity, making it suitable for exploring the geometric response. In the context of two-dimensional electrons in a perpendicular magnetic field, each Landau orbit occupies the same area. The cone geometry naturally provides a structure in which the distances between two adjacent orbits gradually change and can be easily adjusted by altering the tip angle. The presence of a cone tip introduces a geometric singularity that affects the electron density and interacts with the motion of electrons, which has been extensively studied. Furthermore, this type of geometry can automatically create a smooth interface or crossover between the crystalline charge-density-wave state and the liquid-like fractional quantum Hall state. In this work, the properties of this interface are studied from multiple perspectives, shedding light on the behavior of quantum Hall liquids in such geometric configurations.

Engineering magnetic domain wall energies in multiferroic BiFeO$_3$ via epitaxial strain. (arXiv:2311.13215v1 [cond-mat.mtrl-sci])
Sebastian Meyer, Bin Xu, Laurent Bellaiche, Bertrand Dupé

Epitaxial strain has emerged as a powerful tool to tune magnetic and ferroelectric properties in functional materials such as in multiferroic perovskite oxides. Here, we use first-principles calculations to explore the evolution of magnetic interactions in the antiferromagnetic multiferroic BiFeO$_3$ (BFO), one of the most promising multiferroics for future technology. The epitaxial strain in BFO(001) oriented film is varied between $\varepsilon_{xx,yy}$ $\in$ $[-2\%, +2\%]$. We find that both strengths of the exchange interaction and Dzyaloshinskii-Moriya interaction (DMI) decrease linearly from compressive to tensile strain whereas the uniaxial magnetocrystalline anisotropy follows a parabolic behavior which lifts the energy degeneracy of the (111) easy plane of bulk BFO. From the trends of the magnetic interactions we can explain the destruction of cycloidal order in compressive strain as observed in experiments due to the increasing anisotropy energy. For tensile strain, we predict that the ground state remains unchanged as a function of strain. By using the domain wall (DW) energy, we envision the region where isolated chiral magnetic texture might occur as function of strain i.e. where the DW and the spin spiral energy are equal. This transition between $-1.5\%$ and $-0.5\%$ of strain should allow topologically stable magnetic states such as antiferromagnetic skyrmions and merons to occur. Hence, our work should trigger experimental and theoretical investigations in this range of strain.

Controllable orbital angular momentum monopoles in chiral topological semimetals. (arXiv:2311.13217v1 [cond-mat.str-el])
Yun Yen, Jonas A. Krieger, Mengyu Yao, Iñigo Robredo, Kaustuv Manna, Qun Yang, Emily C. McFarlane, Chandra Shekhar, Horst Borrmann, Samuel Stolz, Roland Widmer, Oliver Gröning, Vladimir N. Strocov, Stuart S. P. Parkin, Claudia Felser, Maia G. Vergniory, Michael Schüler, Niels B. M. Schröter

The emerging field of orbitronics aims at generating and controlling currents of electronic orbital angular momentum (OAM) for information processing. Structurally chiral topological crystals could be particularly suitable orbitronic materials because they have been predicted to host topological band degeneracies in reciprocal space that are monopoles of OAM. Around such a monopole, the OAM is locked isotopically parallel or antiparallel to the direction of the electron's momentum, which could be used to generate large and controllable OAM currents. However, OAM monopoles have not yet been directly observed in chiral crystals, and no handle to control their polarity has been discovered. Here, we use circular dichroism in angle-resolved photoelectron spectroscopy (CD-ARPES) to image OAM monopoles in the chiral topological semimetals PtGa and PdGa. Moreover, we also demonstrate that the polarity of the monopole can be controlled via the structural handedness of the host crystal by imaging OAM monopoles and anti-monopoles in the two enantiomers of PdGa, respectively. For most photon energies used in our study, we observe a sign change in the CD-ARPES spectrum when comparing positive and negative momenta along the light direction near the topological degeneracy. This is consistent with the conventional view that CD-ARPES measures the projection of the OAM monopole along the photon momentum. For some photon energies, however, this sign change disappears, which can be understood from our numerical simulations as the interference of polar atomic OAM contributions, consistent with the presence of OAM monopoles. Our results highlight the potential of chiral crystals for orbitronic device applications, and our methodology could enable the discovery of even more complicated nodal OAM textures that could be exploited for orbitronics.

Microstructured organic cavities with high-reflective flat reflectors fabricated by using a nanoimprint-bonding process. (arXiv:2311.13248v1 [physics.optics])
Takuya Enna, Yuji Adachi, Tsukasa Hirao, Shun Takahashi, Yohei Yamamoto, Kenichi Yamashita

The integration of photonic microstructure into organic microcavities represents an effective strategy for manipulating eigenstates of cavity or polariton modes. However, well-established fabrication processes for microstructured organic microcavities are still lacking. In this study, we propose a nanoimprint-bonding process as a novel fabrication method for microstructured organic microcavities. This process relies on a UV nanoimprint technique utilizing two different photopolymer resins, enabling the independent fabrication of highly reflective reflectors and photonic microstructures without compromising the accuracy of each. The resulting organic microcavities demonstrate spatially localized photonic modes within dot structures and their nonlinear responses on the pumping fluence. Furthermore, a highly precise photonic band is confirmed within a honeycomb lattice structure, which is owing to the high quality factor of the cavity achievable with the nanoimprint-bonding process. Additionally, a topological edge state is also observable within a zigzag lattice structure. These results highlight the significant potential of our fabrication method for advancing organic-based photonic devices, including lasers and polariton devices.

Kardar-Parisi-Zhang fluctuations in the synchronization dynamics of limit-cycle oscillators. (arXiv:2311.13253v1 [cond-mat.stat-mech])
Ricardo Gutiérrez, Rodolfo Cuerno

The space-time process whereby one-dimensional systems of self-sustained oscillators synchronize is shown to display generic scale invariance, with scaling properties characteristic of the Kardar-Parisi-Zhang equation with columnar noise, and phase fluctuations that follow a Tracy-Widom probability distribution. This is revealed by a numerical exploration of rings of Stuart-Landau oscillators (the universal representation of an oscillating system close to a Hopf bifurcation) and rings of van der Pol oscillators, both of which are paradigms of self-sustained oscillators. The critical behavior is very well-defined for limit-cycle oscillations near the bifurcation point, and still dominates the behavior comparatively far from the bifurcation. In particular, the Tracy-Widom fluctuation distribution seems to be an extremely robust feature of the synchronization process. The nonequilibrium criticality here described appears to transcend the details of the coupled dynamical systems that synchronize, making plausible its experimental observation.

Buildup and dephasing of Floquet-Bloch bands on subcycle time scales. (arXiv:2311.13309v1 [cond-mat.mes-hall])
S. Ito, M. Schüler, M. Meierhofer, S. Schlauderer, J. Freudenstein, J. Reimann, D. Afanasiev, K. A. Kokh, O. E. Tereshchenko, J. Güdde, M. A. Sentef, U. Höfer, R. Huber

Strong light fields have created spectacular opportunities to tailor novel functionalities of solids. Floquet-Bloch states can form under periodic driving of electrons and enable exotic quantum phases. On subcycle time scales, lightwaves can simultaneously drive intraband currents and interband transitions, which enable high-harmonic generation (HHG) and pave the way towards ultrafast electronics. Yet, the interplay of intra- and interband excitations as well as their relation with Floquet physics have been key open questions as dynamical aspects of Floquet states have remained elusive. Here we provide this pivotal link by pioneering the ultrafast buildup of Floquet-Bloch bands with time- and angle-resolved photoemission spectroscopy. We drive surface states on a topological insulator with mid-infrared fields - strong enough for HHG - and directly monitor the transient band structure with subcycle time resolution. Starting with strong intraband currents, we observe how Floquet sidebands emerge within a single optical cycle; intraband acceleration simultaneously proceeds in multiple sidebands until high-energy electrons scatter into bulk states and dissipation destroys the Floquet bands. Quantum nonequilibrium calculations explain the simultaneous occurrence of Floquet states with intra- and interband dynamics. Our joint experiment-theory study opens up a direct time-domain view of Floquet physics and explores the fundamental frontiers of ultrafast band-structure engineering.

Rashba-splitting-induced topological flat band detected by anomalous resistance oscillations beyond the quantum limit in ZrTe$_5$. (arXiv:2311.13346v1 [cond-mat.mes-hall])
Dong Xing, Bingbing Tong, Senyang Pan, Zezhi Wang, Jianlin Luo, Jinglei Zhang, Cheng-Long Zhang

Topological flat band, on which the kinetic energy of topological electrons is quenched, represents a platform for investigating the topological properties of correlated systems. Recent experimental studies on flattened electronic bands have mainly concentrated on 2-dimensional materials created by van der Waals heterostructure-based engineering. Here, we report the observation of a topological flat band formed by polar-distortion-assisted Rashba splitting in a 3-dimensional Dirac material ZrTe$_5$. The polar distortion and resulting Rashba splitting on the band are directly detected by torque magnetometry and the anomalous Hall effect, respectively. The local symmetry breaking further flattens the band, on which we observe resistance oscillations beyond the quantum limit. These oscillations follow the temperature dependence of the Lifshitz-Kosevich formula but are evenly distributed in B instead of 1/B in high magnetic fields. Furthermore, the cyclotron mass anomalously gets enhanced about 10$^2$ times at field ~20 T. These anomalous properties of oscillations originate from a topological flat band with quenched kinetic energy. The topological flat band, realized by polar-distortion-assisted Rashba splitting in the 3-dimensional Dirac system ZrTe$_5$, signifies an intrinsic platform without invoking moir\'e or order-stacking engineering, and also opens the door for studying topologically correlated phenomena beyond the dimensionality of two.

Wetting and Strain Engineering of 2D Materials on Nanopatterned Substrates. (arXiv:2311.13399v1 [cond-mat.mes-hall])
Davoud Adinehloo, Joshua R. Hendrickson, Vasili Perebeinos

The fascinating realm of strain engineering and wetting transitions in two-dimensional (2D) materials takes place when placed on a two-dimensional array of nanopillars or one-dimensional rectangular grated substrates. Our investigation encompasses a diverse set of atomically thin 2D materials, including transition metal dichalcogenides, hexagonal boron nitride, and graphene, with a keen focus on the impact of van der Waals adhesion energies to the substrate on the wetting/dewetting behavior on nanopatterned substrates. We find a critical aspect ratio of the nanopillar or grating heights to the period of the pattern when the wetting/dewetting transition occurs. Furthermore, energy hysteresis analysis reveals dynamic detachment and re-engagement events during height adjustments, shedding light on energy barriers of 2D monolayer transferred on patterned substrates. Our findings offer avenues for strain engineering in 2D materials, leading to promising prospects for future technological applications.

Triple-sinusoid hedgehog lattice in a centrosymmetric Kondo metal. (arXiv:2311.13405v1 [cond-mat.str-el])
Soohyeon Shin, Jin-Hong Park, Romain Sibille, Harim Jang, Tae Beom Park, Suyoung Kim, Tian Shang, Marisa Medarde, Eric D. Bauer, Oksana Zaharko, Michel Kenzelmann, Tuson Park

Superposed symmetry-equivalent magnetic ordering wave vectors can lead to topologically non-trivial spin textures, such as magnetic skyrmions and hedgehogs, and give rise to novel quantum phenomena due to fictitious magnetic fields associated with a non-zero Berry curvature of these spin textures. To date, all known spin textures are constructed through the superposition of multiple spiral orders, where spins vary in directions with constant amplitude. Recent theoretical studies have suggested that multiple sinusoidal orders, where collinear spins vary in amplitude, can construct distinct topological spin textures regarding chirality properties. However, such textures have yet to be experimentally realised. In this work, we report the observation of a zero-field magnetic hedgehog lattice from a superposition of triple sinusoidal wave vectors in the magnetically frustrated Kondo lattice CePtAl4Ge2. Notably, we also observe the emergence of anomalous electrical and thermodynamic behaviours near the field-induced transition from the zero-field topological hedgehog lattice to a non-topological sinusoidal state. These observations highlight the role of Kondo coupling in stabilising the zero-field hedgehog state in the Kondo lattice and warrant an expedited search for other topological magnetic structures coupled with Kondo coupling.

State Diagrams to determine Tree Tensor Network Operators. (arXiv:2311.13433v1 [quant-ph])
Richard M. Milbradt, Qunsheng Huang, Christian B. Mendl

This work is concerned with tree tensor network operators (TTNOs) for representing quantum Hamiltonians. We first establish a mathematical framework connecting tree topologies with state diagrams. Based on these, we devise an algorithm for constructing a TTNO given a Hamiltonian. The algorithm exploits the tensor product structure of the Hamiltonian to add paths to a state diagram, while combining local operators if possible. We test the capabilities of our algorithm on random Hamiltonians for a given tree structure. Additionally, we construct explicit TTNOs for nearest neighbour interactions on a tree topology. Furthermore, we derive a bound on the bond dimension of tensor operators representing arbitrary interactions on trees. Finally, we consider an open quantum system in the form of a Heisenberg spin chain coupled to bosonic bath sites as a concrete example. We find that tree structures allow for lower bond dimensions of the Hamiltonian tensor network representation compared to a matrix product operator structure. This reduction is large enough to reduce the number of total tensor elements required as soon as the number of baths per spin reaches $3$.

Variable-temperature lightwave-driven scanning tunneling microscope with a compact, turn-key terahertz source. (arXiv:2311.13456v1 [cond-mat.mes-hall])
Hüseyin Azazoglu, Philip Kapitza, Martin Mittendorff, Rolf Möller, Manuel Gruber

We report on a lightwave-driven scanning tunneling microscope based on a home-built microscope and a compact, commercial, and cost-effective terahertz-generation unit with a repetition rate of 100 MHz. The measurements are performed in ultrahigh vacuum at temperatures between 10 K and 300 K. The cross-correlation of the pump and probe pulses indicate a temporal resolution on the order of a picosecond. In terms of spatial resolution, CO molecules, step edges and atomically resolved terraces are readily observed in terahertz images, with sometimes better contrast than in the topographic and (DC) current channels. The utilization of a compact, turn-key terahertz-generation system requires only limited experience with optics and terahertz generation, which may facilitate the deployment of the technique to further research groups.

Controlling crystal cleavage in Focused Ion Beam shaped specimens for surface spectroscopy. (arXiv:2311.13458v1 [cond-mat.mtrl-sci])
A. Hunter, C. Putzke, I. Gaponenko, A. Tamai, F. Baumberger, P.J.W. Moll

Our understanding of quantum materials is commonly based on precise determinations of their electronic spectrum by spectroscopic means, most notably angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM). Both require atomically clean and flat crystal surfaces which traditionally are prepared by in-situ mechanical cleaving in ultrahigh vacuum chambers. We present a new approach that addresses three main issues of the current state-of-the-art methods: 1) Cleaving is a highly stochastic and thus inefficient process; 2) Fracture processes are governed by the bonds in a bulk crystal, and many materials and surfaces simply do not cleave; 3) The location of the cleave is random, preventing data collection at specified regions of interest. Our new workflow is based on Focused Ion Beam (FIB) machining of micro-stress lenses in which shape (rather than crystalline) anisotropy dictates the plane of cleavage, which can be placed at a specific target layer. As proof-of-principle we show ARPES results from micro-cleaves of Sr$_2$RuO$_4$ along the ac plane and from two surface orientations of SrTiO$_3$, a notoriously difficult to cleave cubic perovskite.

Exploring Seiberg-like Dualities with Eight Supercharges. (arXiv:2210.04921v4 [hep-th] UPDATED)
Anindya Dey

We propose a family of IR dualities for 3d $\mathcal{N}=4$ $U(N)$ SQCD with $N_f$ fundamental flavors and $P$ Abelian hypermultiplets i.e. $P$ hypermultiplets in the determinant representation of the gauge group. These theories are good in the Gaiotto-Witten sense if the number of fundamental flavors obeys the constraint $N_f \geq 2N-1$ with generic $P \geq 1$, and in contrast to the standard $U(N)$ SQCD, they do not admit an ugly regime. The IR dualities in question arise in the window $N_f=2N+1,2N,2N-1,$ with $P=1$ in the first case and generic $P \geq 1$ for the others. The dualities involving $N_f=2N \pm 1$ are characterized by an IR enhancement of the Coulomb branch global symmetry on one side of the duality, such that the rank of the emergent global symmetry group is greater than the rank of the UV global symmetry. The dual description makes the rank of this emergent global symmetry manifest in the UV. In addition, one can read off the emergent global symmetry itself from the dual quiver. We show that these dualities are related by certain field theory operations and assemble themselves into a duality web. Finally, we show that the $U(N)$ SQCDs with $N_f \geq 2N-1$ and $P$ Abelian hypers have Lagrangian 3d mirrors, and this allows one to explicitly write down the 3d mirror associated with a given IR dual pair. This paper is the first in a series of four papers on 3d $\mathcal{N}=4$ Seiberg-like dualities.

Pair-Kondo effect: a mechanism for time-reversal broken superconductivity in UTe$_2$. (arXiv:2210.16293v2 [cond-mat.supr-con] UPDATED)
Tamaghna Hazra, Pavel A. Volkov

An important open puzzle in the superconductivity of UTe$_2$ is the emergence of time-reversal broken superconductivity from a non-magnetic normal state. Breaking time-reversal symmetry in a single second-order superconducting transition requires the existence of two degenerate superconducting order parameters, which is not natural for orthorhombic UTe$_2$. Moreover, experiments under pressure (Braithwaite et. al., Comm. Phys. \bf{2}, 147 (2019), arXiv:1909.06074 [cond-mat.str-el]) suggest that superconductivity sets in at a single transition temperature in a finite parameter window, in contrast to the splitting between the symmetry breaking temperatures expected for accidental degenerate orders. Motivated by these observations, we propose a mechanism for the emergence of time-reversal breaking superconductivity without accidental or symmetry-enforced order parameter degeneracies in systems close to a magnetic phase transition. We demonstrate using Landau theory that a cubic coupling between incipient magnetic order and magnetic moments of Cooper pairs (pair-Kondo coupling) can drive time-reversal symmetry breaking superconductivity that onsets in a single, weakly first order transition over an extended region of the phase diagram. We discuss the experimental signatures of such transition in thermodynamic and resonant ultrasound measurements. A microscopic origin of pair-Kondo coupling is identified as screening of magnetic moments by chiral Cooper pairs, built out of two non-degenerate order parameters - an extension of Kondo screening to unconventional pairs.

Full Classification of Transport on an Equilibrated 5/2 Edge via Shot Noise. (arXiv:2212.05732v3 [cond-mat.mes-hall] UPDATED)
Sourav Manna, Ankur Das, Moshe Goldstein, Yuval Gefen

The nature of the bulk topological order of the 5/2 non-Abelian fractional quantum Hall state and the steady-state of its edge are long-studied questions. The most promising non-Abelian model bulk states are the Pfaffian (Pf), anti-Pffafian (APf), and particle-hole symmetric Pfaffian (PHPf). Here, we propose to employ a set of dc current-current correlations \emph{(electrical shot noise)} in order to distinguish among the Pf, APf, and PHPf candidate states, as well as to determine their edge thermal equilibration regimes: full vs.\ partial. Using other tools, measurements of GaAs platforms have already indicated consistency with the PHPf state. Our protocol, realizable with available experimental tools, is based on fully electrical measurements.

Evidence for three-dimensional Dirac semimetal state in strongly correlated organic quasi-two-dimensional material. (arXiv:2302.05616v2 [cond-mat.str-el] UPDATED)
Naoya Tajima, Yoshitaka Kawasugi, Takao Morinari, Ryuhei Oka, Toshio Naito, Reizo Kato

The three-dimensional Dirac semimetal is distinct from its two-dimensional counterpart due to its dimensionality and symmetry. Here, we observe that molecule-based quasi-two-dimensional Dirac fermion system, $\alpha$-(BEDT-TTF)$_2$I$_3$, exhibits chiral anomaly-induced negative magnetoresistance and planar Hall effect upon entering the coherent inter-layer tunneling regime under high pressure. Time-reversal symmetry is broken due to the strong electronic correlation effect, while the spin-orbit coupling effect is negligible. The system provides an ideal platform for investigating the chiral anomaly physics by controlling dimensionality and strong electronic correlation.

Extracting higher central charge from a single wave function. (arXiv:2303.04822v4 [cond-mat.str-el] UPDATED)
Ryohei Kobayashi, Taige Wang, Tomohiro Soejima, Roger S. K. Mong, Shinsei Ryu

A (2+1)D topologically ordered phase may or may not have a gappable edge, even if its chiral central charge $c_-$ is vanishing. Recently, it is discovered that a quantity regarded as a "higher" version of chiral central charge gives a further obstruction beyond $c_-$ to gapping out the edge. In this Letter, we show that the higher central charges can be characterized by the expectation value of the \textit{partial rotation} operator acting on the wavefunction of the topologically ordered state. This allows us to extract the higher central charge from a single wavefunction, which can be evaluated on a quantum computer. Our characterization of the higher central charge is analytically derived from the modular properties of edge conformal field theory, as well as the numerical results with the $\nu=1/2$ bosonic Laughlin state and the non-Abelian gapped phase of the Kitaev honeycomb model, which corresponds to $\mathrm{U}(1)_2$ and Ising topological order respectively. The letter establishes a numerical method to obtain a set of obstructions to the gappable edge of (2+1)D bosonic topological order beyond $c_-$, which enables us to completely determine if a (2+1)D bosonic Abelian topological order has a gappable edge or not. We also point out that the expectation values of the partial rotation on a single wavefunction put a constraint on the low-energy spectrum of the bulk-boundary system of (2+1)D bosonic topological order, reminiscent of the Lieb-Schultz-Mattis type theorems.

Anomalous second-order skin modes in Floquet non-Hermitian systems. (arXiv:2303.11259v2 [cond-mat.mes-hall] UPDATED)
Chun-Hui Liu, Haiping Hu, Shu Chen, Xiong-Jun Liu

The non-Hermitian skin effect under open boundary conditions is widely believed to originate from the intrinsic spectral topology under periodic boundary conditions. If the eigenspectra under periodic boundary conditions have no spectral windings (e.g., piecewise arcs) or a finite area on the complex plane, there will be no non-Hermitian skin effect with open boundaries. In this article, we demonstrate another scenario beyond this perception by introducing a two-dimensional periodically driven model. The effective Floquet Hamiltonian lacks intrinsic spectral topology and is proportional to the identity matrix (representing a single point on the complex plane) under periodic boundary conditions. Yet, the Floquet Hamiltonian exhibits a second-order skin effect that is robust against perturbations and disorder under open boundary conditions. We further reveal the dynamical origin of these second-order skin modes and illustrate that they are characterized by a dynamical topological invariant of the full time-evolution operator.

Edge-selective extremal damping from topological heritage of dissipative Chern insulators. (arXiv:2304.09040v2 [cond-mat.mes-hall] UPDATED)
Suraj S. Hegde, Toni Ehmcke, Tobias Meng

One of the most important practical hallmarks of topological matter is the presence of topologically protected, exponentially localised edge states at interfaces of regions characterised by unequal topological invariants. Here, we show that even when driven far from their equilibrium ground state, Chern insulators can inherit topological edge features from their parent Hamiltonian. In particular, we show that the asymptotic long-time approach of the non-equilibrium steady state, governed by a Lindblad Master equation, can exhibit edge-selective extremal damping. This phenomenon derives from edge states of non-Hermitian extensions of the parent Chern insulator Hamiltonian. The combination of (non-Hermitian) topology and dissipation hence allows to design topologically robust, spatially localised damping patterns.

Roses in the Nonperturbative Current Response of Artificial Crystals. (arXiv:2305.03013v2 [cond-mat.mes-hall] UPDATED)
Christophe De Beule, Vo Tien Phong, E. J. Mele

In two-dimensional artificial crystals with large real-space periodicity, the nonlinear current response to a large applied electric field can feature a strong angular dependence, which encodes information about the band dispersion and Berry curvature of isolated electronic Bloch minibands. Within the relaxation-time approximation, we obtain analytic expressions up to infinite order in the driving field for the current in a band-projected theory with time-reversal and trigonal symmetry. For a fixed field strength, the dependence of the current on the direction of the applied field is given by rose curves whose petal structure is symmetry constrained and is obtained from an expansion in real-space translation vectors. We illustrate our theory with calculations on periodically-buckled graphene and twisted double bilayer graphene, wherein the discussed physics can be accessed at experimentally-relevant field strengths.

Topological interface states -- a possible path towards a Landau-level laser in the THz regime. (arXiv:2307.05116v4 [cond-mat.mes-hall] UPDATED)
Mark O. Goerbig

Volkov-Pankratov surface bands arise in smooth topological interfaces, i.e. interfaces between a topological and a trivial insulator, in addition to the chiral surface state imposed by the bulk-surface correspondence of topological materials. These two-dimensional bands become Landau-quantized if a magnetic field is applied perpendicular to the interface. I show that the energy scales, which are typically in the 10-100 meV range, can be controlled both by the perpendicular magnetic field and the interface width. The latter can still be varied with the help of a magnetic-field component in the interface. The Landau levels of the different Volkov-Pankratov bands are optically coupled, and their arrangement may allow one to obtain population inversion by resonant optical pumping. This could serve as the elementary brick of a multi-level laser based on Landau levels. Moreover, the photons are absorbed and emitted either parallel or perpendicular to the magnetic field, respectively in the Voigt and Faraday geometry, depending on the Volkov-Pankratov bands and Landau levels involved in the optical transitions.

Spin-Peierls instability of the U(1) Dirac spin liquid. (arXiv:2307.12295v3 [cond-mat.str-el] UPDATED)
Urban F. P. Seifert, Josef Willsher, Markus Drescher, Frank Pollmann, Johannes Knolle

A complicating factor in the realization and observation of quantum spin liquids in materials is the ubiquitous presence of other degrees of freedom, in particular lattice distortion modes (phonons). These provide additional routes for relieving magnetic frustration, thereby possibly destabilizing spin-liquid ground states. In this work, we focus on triangular-lattice Heisenberg antiferromagnets, where recent numerical evidence suggests the presence of an extended U(1) Dirac spin liquid phase which is described by compact quantum electrodynamics in 2+1 dimensions (QED$_3$), featuring gapless spinons and monopoles as gauge excitations, and believed to flow to a strongly-coupled fixed point with conformal symmetry. Using complementary perturbation theory and scaling arguments, we show that a symmetry-allowed coupling between (classical) finite-wavevector lattice distortions and monopole operators of the U(1) Dirac spin liquid generally induces a spin-Peierls instability towards a (confining) 12-site valence-bond solid state. We support our theoretical analysis with state-of-the-art density matrix renormalization group simulations. Away from the limit of static distortions, we demonstrate that the phonon energy gap establishes a parameter regime where the spin liquid is expected to be stable, and show that the monopole-lattice coupling leads to softening of the phonon in analogy to the Kohn anomaly. We discuss the applicability of our results to similar systems, in particular the Dirac spin liquid on the Kagome lattice.

The mass of simple and higher-order networks. (arXiv:2309.07851v3 [cond-mat.dis-nn] UPDATED)
Ginestra Bianconi

We propose a theoretical framework that explains how the mass of simple and higher-order networks emerges from their topology and geometry. We use the discrete topological Dirac operator to define an action for a massless self-interacting topological Dirac field inspired by the Nambu-Jona Lasinio model. The mass of the network is strictly speaking the mass of this topological Dirac field defined on the network; it results from the chiral symmetry breaking of the model and satisfies a self-consistent gap equation. Interestingly, it is shown that the mass of a network depends on its spectral properties, topology, and geometry. Due to the breaking of the matter-antimatter symmetry observed for the harmonic modes of the discrete topological Dirac operator, two possible definitions of the network mass can be given. For both possible definitions, the mass of the network comes from a gap equation with the difference among the two definitions encoded in the value of the bare mass. Indeed, the bare mass can be determined either by the Betti number $\beta_0$ or by the Betti number $\beta_1$ of the network. We provide numerical results on the mass of different networks, including random graphs, scale-free, and real weighted collaboration networks. We also discuss the generalization of these results to higher-order networks, defining the mass of simplicial complexes. The observed dependence of the mass of the considered topological Dirac field with the topology and geometry of the network could lead to interesting physics in the scenario in which the considered Dirac field is coupled with a dynamical evolution of the underlying network structure.

Mapping of Spin-Wave Transport in Thulium Iron Garnet Thin Films Using Diamond Quantum Microscopy. (arXiv:2310.06188v3 [cond-mat.mes-hall] UPDATED)
Rupak Timalsina, Haohan Wang, Bharat Giri, Adam Erickson, Xiaoshan Xu, Abdelghani Laraoui

Spin waves, collective dynamic magnetic excitations, offer crucial insights into magnetic material properties. Rare-earth iron garnets offer an ideal spin-wave (SW) platform with long propagation length, short wavelength, gigahertz frequency, and applicability to magnon spintronic platforms. Of particular interest, thulium iron garnet (TmIG) has attracted a huge interest recently due to its successful growth down to a few nanometers, observed topological Hall effect and spin orbit torque-induced switching effects. However, there is no direct spatial measurement of its SW properties. This work uses diamond nitrogen vacancy (NV) magnetometry in combination with SW electrical transmission spectroscopy to study SW transport properties in TmIG thin films. NV magnetometry allows probing spin waves at the sub-micrometer scale, seen by the amplification of the local microwave magnetic field due to the coupling of NV spin qubits with the stray magnetic field produced by the microwave-excited spin waves. By monitoring the NV spin resonances, the SW properties in TmIG thin films are measured as function of the applied magnetic field, including their amplitude, decay length (~ 50 um), and wavelength (0.8 - 2 um). These results pave the way for studying spin qubit-magnon interactions in rare-earth magnetic insulators, relevant to quantum magnonics applications.

Astronomical Infrared Bands and Diffuse Interstellar Bands Both Reproduced by Hydrocarbon Pentagon-Hexagon Combined PAH Molecules. (arXiv:2310.06264v2 [astro-ph.GA] UPDATED)
Norio Ota

This study theoretically predicts the specific Polycyclic Aromatic Hydrocarbon (PAH) molecules to reproduce both astronomically observed Infrared Bands (IR) and Diffuse Interstellar Bands (DIB). In our recent paper, we could reproduce IR by the hydrocarbon pentagon-hexagon combined PAH molecules using Density Functional Theory (DFT). Found molecules were (C53H18), and (C23H12) with two carbon pentagons among hexagon networks. Origin of DIB may come from the molecular orbital excitation. We applied Time-Dependent DFT calculation. In case of (C53H18), by comparing calculation with observed DIB, we found 7 coincide bands among 42 calculated bands within observed band width. For example, neutral (C53H18) shows calculated 577.35nm band coincide well with observed DIB at 577.95nm within 1.55nm observed band width. Mono-cation shows calculated 627.87nm correspond to observed 627.83nm, also for di-cation calculated 635.89nm to observed 635.95nm. For smaller size molecule (C23H12), we found 5 coincide bands, of which mono-cation shows calculated 713.92nm coincide with observed 713.80nm, di-cation shows calculated 653.27nm correlate to observed 653.21nm. By such quantum-chemical survey, we could predict specific PAH molecules floating in interstellar space.

Higher-group symmetry of (3+1)D fermionic $\mathbb{Z}_2$ gauge theory: logical CCZ, CS, and T gates from higher symmetry. (arXiv:2311.05674v2 [cond-mat.str-el] UPDATED)
Maissam Barkeshli, Po-Shen Hsin, Ryohei Kobayashi

It has recently been understood that the complete global symmetry of finite group topological gauge theories contains the structure of a higher-group. Here we study the higher-group structure in (3+1)D $\mathbb{Z}_2$ gauge theory with an emergent fermion, and point out that pumping chiral $p+ip$ topological states gives rise to a $\mathbb{Z}_{8}$ 0-form symmetry with mixed gravitational anomaly. This ordinary symmetry mixes with the other higher symmetries to form a 3-group structure, which we examine in detail. We then show that in the context of stabilizer quantum codes, one can obtain logical CCZ and CS gates by placing the code on a discretization of $T^3$ (3-torus) and $T^2 \rtimes_{C_2} S^1$ (2-torus bundle over the circle) respectively, and pumping $p+ip$ states. Our considerations also imply the possibility of a logical $T$ gate by placing the code on $\mathbb{RP}^3$ and pumping a $p+ip$ topological state.

Berry curvature induced giant intrinsic spin-orbit torque in single layer magnetic Weyl semimetal thin films. (arXiv:2311.08145v2 [cond-mat.mes-hall] UPDATED)
Lakhan Bainsla, Yuya Sakuraba, Keisuke Masuda, Akash Kumar, Ahmad A. Awad, Nilamani Behera, Roman Khymyn, Saroj Prasad Dash, Johan Åkerman

Topological quantum materials can exhibit unconventional surface states and anomalous transport properties, but their applications to spintronic devices are restricted as they require the growth of high-quality thin films with bulk-like properties. Here, we study 10--30 nm thick epitaxial ferromagnetic Co$_{\rm 2}$MnGa films with high structural order. Very high values of the anomalous Hall conductivity, $\sigma_{\rm xy}=1.35\times10^{5}$ $\Omega^{-1} m^{-1}$, and the anomalous Hall angle, $\theta_{\rm H}=15.8\%$, both comparable to bulk values. We observe a dramatic crystalline orientation dependence of the Gilbert damping constant of a factor of two and a giant intrinsic spin Hall conductivity, $\mathit{\sigma_{\rm SHC}}=(6.08\pm 0.02)\times 10^{5}$ ($\hbar/2e$) $\Omega^{-1} m^{-1}$, which is an order of magnitude higher than literature values of single-layer Ni$_{\rm 80}$Fe$_{\rm 20}$, Ni, Co, Fe, and multilayer Co$_{\rm 2}$MnGa stacks. Theoretical calculations of the intrinsic spin Hall conductivity, originating from a strong Berry curvature, corroborate the results and yield values comparable to the experiment. Our results open up for the design of spintronic devices based on single layers of topological quantum materials.

Found 10 papers in prb
Date of feed: Thu, 23 Nov 2023 04:17:16 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)

Ultrafast control of the crystal structure in a topological charge-density-wave material
Takeshi Suzuki, Yuya Kubota, Natsuki Mitsuishi, Shunsuke Akatsuka, Jumpei Koga, Masato Sakano, Satoru Masubuchi, Yoshikazu Tanaka, Tadashi Togashi, Hiroyuki Ohsumi, Kenji Tamasaku, Makina Yabashi, Hidefumi Takahashi, Shintaro Ishiwata, Tomoki Machida, Iwao Matsuda, Kyoko Ishizaka, and Kozo Okazaki
Author(s): Takeshi Suzuki, Yuya Kubota, Natsuki Mitsuishi, Shunsuke Akatsuka, Jumpei Koga, Masato Sakano, Satoru Masubuchi, Yoshikazu Tanaka, Tadashi Togashi, Hiroyuki Ohsumi, Kenji Tamasaku, Makina Yabashi, Hidefumi Takahashi, Shintaro Ishiwata, Tomoki Machida, Iwao Matsuda, Kyoko Ishizaka, and Kozo Okazaki

The optical control of crystal structures is a promising route to change physical properties including the topological nature of a targeting material. Time-resolved x-ray diffraction measurements using an x-ray free-electron laser are performed to study the ultrafast lattice dynamics of ${\mathrm{VT…

[Phys. Rev. B 108, 184305] Published Wed Nov 22, 2023

Strong magnetic proximity effect in van der Waals heterostructures driven by direct hybridization
C. Cardoso, A. T. Costa, A. H. MacDonald, and J. Fernández-Rossier
Author(s): C. Cardoso, A. T. Costa, A. H. MacDonald, and J. Fernández-Rossier

The conventional spin proximity effect is normally pictured in terms of a small spin splitting of the bands of a nonmagnetic material, due to exchange coupling to a ferromagnet. In this work, the authors show a different type of proximity mechanism, where only one spin channel in the nonmagnetic material becomes strongly hybridized with the ferromagnet, whereas the other remains unaffected. In the case of graphene coupled to CrI3, a ferromagnetic insulator, the authors show that the hybridization proximity is both strong and electrically tunable.

[Phys. Rev. B 108, 184423] Published Wed Nov 22, 2023

Superconductivity and vortex structure in ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}/{\mathrm{FeTe}}_{0.55}{\mathrm{Se}}_{0.45}$ heterostructures with varying ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ thickness
Kailun Chen, Mingyang Chen, Chuanhao Wen, Zhiyong Hou, Huan Yang, and Hai-Hu Wen
Author(s): Kailun Chen, Mingyang Chen, Chuanhao Wen, Zhiyong Hou, Huan Yang, and Hai-Hu Wen

Using scanning tunneling microscopy, we investigate the superconductivity and vortex properties in topological insulator ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ thin films grown on the iron-based superconductor ${\mathrm{FeTe}}_{0.55}{\mathrm{Se}}_{0.45}$. The proximity-induced superconductivity weaken…

[Phys. Rev. B 108, 184512] Published Wed Nov 22, 2023

Orbital-selective chemical functionalization of ${\text{MoS}}_{2}$ by $\mathrm{Fe}$
Niels Ehlen, Yannic Falke, Boris V. Senkovskiy, Timo Knispel, Jeison Fischer, Oliver N. Gallego, Cesare Tresca, Maximilian Buchta, Konstantin P. Shchukin, Alessandro D'Elia, Giovanni Di Santo, Luca Petaccia, Dmitry Smirnov, Anna Makarova, Gianni Profeta, Thomas Michely, and Alexander Grüneis
Author(s): Niels Ehlen, Yannic Falke, Boris V. Senkovskiy, Timo Knispel, Jeison Fischer, Oliver N. Gallego, Cesare Tresca, Maximilian Buchta, Konstantin P. Shchukin, Alessandro D'Elia, Giovanni Di Santo, Luca Petaccia, Dmitry Smirnov, Anna Makarova, Gianni Profeta, Thomas Michely, and Alexander Grüneis

The occupied electron energy bands of monolayer ${\mathrm{MoS}}_{2}$ are composed from out-of-plane $d$ orbitals at the Brillouin zone (BZ) center and from in-plane $d$ orbitals at the BZ corner. If a dopant would interact in an orbital selective manner with the ${\mathrm{MoS}}_{2}$ bands, it could …

[Phys. Rev. B 108, 195430] Published Wed Nov 22, 2023

Investigation of a $+2$ oxidation spin state in weakly doped ${\mathrm{Cd}}_{1−x}{\mathrm{Ti}}_{x}\mathrm{Se}$
J. Dimuna, T. Boyett, I. Miotkowski, A. K. Ramdas, T. M. Pekarek, and J. T. Haraldsen
Author(s): J. Dimuna, T. Boyett, I. Miotkowski, A. K. Ramdas, T. M. Pekarek, and J. T. Haraldsen

Using computational and experimental techniques, we examine the nature of the $+2$ oxidation of titanium (Ti)-doped CdSe. Through stoichiometry and confirmed through magnetization measurements, the weakly doped ${\mathrm{Cd}}_{1−x}{\mathrm{Ti}}_{x}\mathrm{Se}$ $(x=0.000\phantom{\rule{0.16em}{0ex}}43…

[Phys. Rev. B 108, 205202] Published Wed Nov 22, 2023

Breakdown of helical edge state topologically protected conductance in time-reversal-breaking excitonic insulators
Yan-Qi Wang, Michał Papaj, and Joel E. Moore
Author(s): Yan-Qi Wang, Michał Papaj, and Joel E. Moore

Gapless helical edge modes are a hallmark of the quantum spin Hall effect. Protected by time-reversal symmetry, each edge contributes a quantized zero-temperature conductance quantum ${G}_{0}≡{e}^{2}/h$. However, the experimentally observed conductance in ${\mathrm{WTe}}_{2}$ decreases below ${G}_{0…

[Phys. Rev. B 108, 205420] Published Wed Nov 22, 2023

Topological dissipative Kerr soliton combs in a valley photonic crystal resonator
Zhen Jiang, Lefeng Zhou, Wei Li, Yudong Li, Liangsen Feng, Tengfei Wu, Chun Jiang, and Guangqiang He
Author(s): Zhen Jiang, Lefeng Zhou, Wei Li, Yudong Li, Liangsen Feng, Tengfei Wu, Chun Jiang, and Guangqiang He

Topological phases have become an enabling role in exploiting new applications of nonlinear optics in recent years. Here we theoretically propose a valley photonic crystal resonator emulating topologically protected dissipative Kerr soliton combs. It is shown that topological resonator modes can be …

[Phys. Rev. B 108, 205421] Published Wed Nov 22, 2023

Photoluminescence properties and excited state dynamics of monolayer perylene on graphite (0001)
Takashi Yamada
Author(s): Takashi Yamada

The correlation between the photoluminescence properties and excited state dynamics of perylene $({\mathrm{C}}_{20}{\mathrm{H}}_{12})$ formed on a graphite (0001) substrate was investigated at the monolayer limit. Time-resolved two-photon photoemission spectroscopy was used to evaluate the lifetime …

[Phys. Rev. B 108, 205422] Published Wed Nov 22, 2023

Floquet gap-dependent topological classifications from color-decorated frequency lattices with space-time symmetries
Ilyoun Na, Jack Kemp, Sinéad M. Griffin, Robert-Jan Slager, and Yang Peng
Author(s): Ilyoun Na, Jack Kemp, Sinéad M. Griffin, Robert-Jan Slager, and Yang Peng

We find a class of Floquet topological phases exhibiting gap-dependent topological classifications in quantum systems with a dynamical space-time symmetry and an antisymmetry. This is in contrast to all existing Floquet topological phases protected by static symmetries, where the topological classi…

[Phys. Rev. B 108, L180302] Published Wed Nov 22, 2023

${\mathrm{Pb}}_{9}{\mathrm{Cu}({\mathrm{PO}}_{4})}_{6}\mathrm{O}$ is a charge-transfer semiconductor
Lorenzo Celiberti, Lorenzo Varrassi, and Cesare Franchini
Author(s): Lorenzo Celiberti, Lorenzo Varrassi, and Cesare Franchini

By means of density functional theory and constrained random phase approximation we analyze the band structure of ${\mathrm{Pb}}_{9}\mathrm{Cu}{({\mathrm{PO}}_{4})}_{6}\mathrm{O}$ (named LK-99). Our data show that the lead-phosphate apatite LK-99 in the proposed Cu-doped structure is a semiconductor…

[Phys. Rev. B 108, L201117] Published Wed Nov 22, 2023

Found 3 papers in prl
Date of feed: Thu, 23 Nov 2023 04:17:18 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)

Model for Emergence of Spacetime from Fluctuations
Marcus Reitz, Barbara Šoda, and Achim Kempf
Author(s): Marcus Reitz, Barbara Šoda, and Achim Kempf

We use a result of Hawking and Gilkey to define a Euclidean path integral of gravity and matter which has the special property of being independent of the choice of basis in the space of fields. This property allows the path integral to also describe physical regimes that do not admit position bases…

[Phys. Rev. Lett. 131, 211501] Published Wed Nov 22, 2023

Classifying Topology in Photonic Heterostructures with Gapless Environments
Kahlil Y. Dixon, Terry A. Loring, and Alexander Cerjan
Author(s): Kahlil Y. Dixon, Terry A. Loring, and Alexander Cerjan

Photonic topological insulators exhibit bulk-boundary correspondence, which requires that boundary-localized states appear at the interface formed between topologically distinct insulating materials. However, many topological photonic devices share a boundary with free space, which raises a subtle b…

[Phys. Rev. Lett. 131, 213801] Published Wed Nov 22, 2023

Simple Model for Dynamic Heterogeneity in Glass-Forming Liquids
Rajib K. Pandit and Horacio E. Castillo
Author(s): Rajib K. Pandit and Horacio E. Castillo

Liquids near the glass transition exhibit dynamical heterogeneity, i.e., local relaxation rates fluctuate strongly over space and time. Here, we introduce a simple continuum model that allows for quantitative predictions for the correlators describing these fluctuations. We find remarkable agreement…

[Phys. Rev. Lett. 131, 218202] Published Wed Nov 22, 2023

Found 1 papers in pr_res
Date of feed: Thu, 23 Nov 2023 04:17:17 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)

Designing nontrivial one-dimensional Floquet topological phases using a spin-1/2 double-kicked rotor
Yusuke Koyama, Kazuya Fujimoto, Shuta Nakajima, and Yuki Kawaguchi
Author(s): Yusuke Koyama, Kazuya Fujimoto, Shuta Nakajima, and Yuki Kawaguchi

A quantum kicked rotor model is one of the promising systems to realize various Floquet topological phases. We consider a double-kicked rotor model for a one-dimensional quasi-spin-1/2 Bose-Einstein condensate with spin-dependent and spin-independent kicks which are implementable for cold atomic exp…

[Phys. Rev. Research 5, 043167] Published Wed Nov 22, 2023