Found 38 papers in cond-mat
Date of feed: Thu, 21 Dec 2023 01:30:00 GMT

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Nonlinear Thermoelectric Probes of Anomalous Dynamics in Topological Fermi Liquids. (arXiv:2312.12520v1 [cond-mat.mes-hall])
Johannes Hofmann, Habib Rostami

In two-dimensional Fermi liquids, odd-parity Fermi surface deformations have anomalously slow relaxation rates that are suppressed as $T^4$ with temperature $T$, distinct from the standard Fermi-liquid $T^2$ scaling. We demonstrate here that these long-lived modes, which are often hidden in linear response, have a significant impact on nonlinear transport by establishing a direct proportionality of nonlinear thermoelectric currents to the anomalously large relaxation time. These currents exist in topological time-reversal invariant Fermi liquids, and their magnitude is characterized by new topological heat capacitance terms that we refer to as the {\em Berry curvature capacity} and the {\em velocity-curvature capacity}. We quantify the effect in bismuth telluride, which is an efficient thermoelectric and a topological insulator with a hexagonal Fermi surface. Our findings demonstrate the potential to explore topological and many-body effects in Fermi liquids through the nonlinear thermoelectric response, urging further experimental studies.

Topology, magnetism and charge order in twisted MoTe2 at higher integer hole fillings. (arXiv:2312.12531v1 [cond-mat.str-el])
Taige Wang, Minxuan Wang, Woochang Kim, Steven G. Louie, Liang Fu, Michael P. Zaletel

Twisted homobilayer transition metal dichalcogenide (TMD) attracts an expanding experimental interest recently for exhibiting a variety of topological and magnetic states even at zero magnetic field. Most of the studies right now focus on hole filling nu_h < 1, while a rich phase diagram at higher hole filling calls for more investigation. We perform a thorough survey of possible interaction-driven phases at higher integer hole fillings. We first construct the continuum model from a first-principles calculation, and then perform a self-consistent Hartree-Fock study of the interacting ground states. We identify various valley polarized (VP) states at odd integer fillings and intervalley coherent (IVC) states at even integer fillings and discuss the energetics competition among them. We also discuss the origin and the experimental implications of the curious Chern insulator at nu_h = 2.

Conformal field theories in a magnetic field. (arXiv:2312.12546v1 [hep-th])
Rufus Boyack, Luca V. Delacrétaz, Éric Dupuis, William Witczak-Krempa

We study the properties of 2+1d conformal field theories (CFTs) in a background magnetic field. Using generalized particle-vortex duality, we argue that in many cases of interest the theory becomes gapped, which allows us to make a number of predictions for the magnetic response, background monopole operators, and more. Explicit calculations at large N for Wilson-Fisher and Gross-Neveu CFTs support our claim, and yield the spectrum of background (defect) monopole operators. Finally, we point out that other possibilities exist: certain CFTs can become metallic in a magnetic field. Such a scenario occurs for a Dirac fermion coupled to a Chern-Simons gauge field, where a non-Fermi liquid is argued to emerge.

A degenerate trion liquid in atomic double layers. (arXiv:2312.12571v1 [cond-mat.mes-hall])
Phuong X. Nguyen, Raghav Chaturvedi, Liguo Ma, Patrick Knuppel, Kenji Watanabe, Takashi Taniguchi, Kin Fai Mak, Jie Shan

Trions are a three-particle bound state of electrons and holes. Experimental realization of a trion liquid in the degenerate quantum limit would open a wide range of phenomena in quantum many-body physics. However, trions have been observed only as optically excited states in doped semiconductors to date. Here we report the emergence of a degenerate trion liquid in a Bose-Fermi mixture of holes and excitons in Coulomb-coupled MoSe2/WSe2 monolayers. By electrically tuning the hole density in WSe2 to be two times the electron density in MoSe2, we generate equilibrium interlayer trions with binding energy about 1 meV at temperatures two orders of magnitude below the Fermi temperature. We further demonstrate a density-tuned phase transition to an electron-hole plasma, spin-singlet correlations for the constituent holes and Zeeman-field-induced dissociation of trions. The results pave the way for exploration of the correlated phases of composite particles in solids.

Graph Theorem for Chiral Exact Flat Bands at Charge Neutrality. (arXiv:2312.12607v1 [cond-mat.mtrl-sci])
Gurjyot Sethi, Bowen Xia, Dongwook Kim, Hang Liu, Xiaoyin Li, Feng Liu

Chiral exact flat bands (FBs) at charge neutrality have attracted much recent interest, presenting an intriguing condensed-matter system to realize exact many-body phenomena, as specifically shown in "magic angle" twisted bilayer graphene for superconductivity and triangulene-based superatomic graphene for excitonic condensation. Yet, no generic physical model to realize such FBs has been developed. Here we present a new mathematical theorem, called bipartite double cover (BDC) theorem, and prove that the BDC of line-graph (LG) lattices hosts at least two chiral exact FBs of opposite chirality, i.e., yin-yang FBs, centered-around/at charge neutrality (E = 0) akin to the "chiral limit" of twisted bilayer graphene. We illustrate this theorem by mapping it exactly onto tight-binding lattice models of the BDC of LGs of hexagonal lattice for strong topological and of triangular lattice for fragile topological FBs, respectively. Moreover, we use orbital design principle to realize such exotic yin-yang FBs in non-BDC lattices to instigate their real material discovery. This work not only enables the search for exact chiral FBs at zero energy beyond moir\'e heterostructures, but also opens the door to discovering quantum semiconductor features with FB-enabled strongly correlated carriers.

Nematic charge-density-wave correlations in FeSe$_{1-x}$S$_{x}$. (arXiv:2312.12749v1 [cond-mat.supr-con])
Ruixian Liu, Wenliang Zhang, Yuan Wei, Zhen Tao, Teguh C. Asmara, Vladimir N. Strocov, Thorsten Schmitt, Xingye Lu

The occurrence of charge-density-wave (CDW) order is a common thread in the phase diagram of cuprate high-transition-temperature ($T_c$) superconductors. In iron-based superconductors (FeSCs), nematic order and fluctuations play a decisive role in driving other emergent orders. CDW order has been observed by scanning tunneling microscopy for various FeSCs such as FeSe thin films, uniaxially strained LiFeAs, and tetragonal FeSe$_{0.81}$S$_{0.19}$. However, it remains elusive if the CDW in these materials is a bulk phenomenon as well as if and how it intertwines with the electronic nematicity. Using energy-resolved resonant X-ray scattering at the Fe-L$_3$ edge, we report the discovery of a local-strain-induced incommensurate isotropic CDW order in FeSe$_{0.82}$S$_{0.18}$. A highly anisotropic CDW response under uniaxial strain unambiguously manifests that the CDW is directly coupled to the nematicity. Transforming part of Fe$^{2+}$ to Fe$^{3+}$ on the surface of {\FSS} reveals that the same isotropic CDW can be induced, enhanced, and stabilized in the whole nematic regime measured ($x=0-0.19$). As Fe$^{3+}$ can create local lattice distortions on the surface, the CDW could arise from the interaction between the local strain around Fe$^{3+}$ and the nematic electron correlations. Our experimental observation of a local-strain-induced CDW gives vital information for understanding the interplay between electron correlations and the electronic nematicity in FeSCs.

Twisted topology and Bipolar Non-Hermitian Skin Effect induced by long-range asymmetric coupling. (arXiv:2312.12780v1 [cond-mat.mes-hall])
S. M. Rafi-Ul-Islam, Zhuo Bin Siu, Haydar Sahin, Md. Saddam Hossain Razo, Mansoor B. A. Jalil

We investigate the twisted topology of the complex eigenspectrum of a one-dimensional non-Hermitian system under the influence of long-range unidirectional coupling. Unlike the complex energy spectrum of the conventional Hatano-Nelson chain, which takes the form of a single loop with a topological winding index of a definite sign, the introduction of long-range unidirectional hopping results in the creation of multiple twisted loops. These twisted loops exhibit opposite signs of the topological winding index, which correlate to alternating clockwise and anticlockwise energy windings. The simultaneous presence of both signs of the winding index translates into a bipolar non-Hermitian skin effect (NHSE), which challenges the conventional wisdom that the NHSE localization is dependent on the direction of the dominant nearest-neighbor interactions. In this bipolar NHSE, the exponents of the complex energy eigenvectors corresponding to clockwise and anti-clockwise windings, lie inside and outside of the complex unit circle, respectively. Interestingly, at the intersections of oppositely oriented energy loops where the sign of the topological winding index flips, the energy becomes real-valued, leading to a suppression of the NHSE. This marks the emergence of Bloch-like contact points, where both the bipolar NHSE and the traditional NHSE vanish. Based on the non-Hermitian model we provide analytical insights into the effects of long-range unidirectional coupling to the winding topology of its complex energy spectra and their broader implications for the field of condensed matter physics.

Strain-driven Charge Localisation and Spin Dynamics of Paramagnetic Defects in S-deficit 2H-MoS2 Nanocrystals. (arXiv:2312.12805v1 [cond-mat.mtrl-sci])
Sudipta Khamrui, Kamini Bharti, Daniella Goldfarb, Tilak Das, Debamalya Banerjee

A microscopic control over the origin and dynamics of localised spin centres in lower dimensional solids turns out to be a key factor for next generation spintronics and quantum technologies. With the help of low temperature electron paramagnetic resonance (EPR) measurements, supported by the first-principles calculations within density functional theory (DFT) formulation, we found the origin of different high-spin paramagnetic intrinsic charge-centres, Mo3+(4d3) and Mo2+(4d4) present in the nano-crystalline sulfur deficit hexagonal molybdenum disulfide (2H-MoS_(2-x)), against the established notion of spin-1/2 , Mo5+ centres. A critical strain generated in the nano-structured 2H-MoS_(2-x) was found to be very crucial for spin-localization in this layered material. Indeed, computationally effective proposition of the PBE+U exchange-correlations within DFT including D3-dispersion corrections found to be more viable than expensive higher rung of exchange-correlation functionals, explored earlier. It is also found that the oxygen vacancy of the reduced oxide phase, embedded in 2H-MoS_(2-x) host lattice, has the longest relaxation times. Moreover, the temperature dependence of spin-lattice relaxation measurements reveals a direct process for interstitial spin centres and a Raman process for both sulfur and oxygen vacancy sites. We expect such observation would be a valuable pillar for better understanding of the next generation quantum technologies and device applications.

Li-decorated BC3 nanopores: Promising materials for hydrogen storage. (arXiv:2312.12841v1 [cond-mat.mtrl-sci])
I. Cabria, A. Lebon, M. B. Torres, L. J. Gallego, A. Vega

In the quest of new absorbent for hydrogen storage, we investigate the capacities of slit pores formed by two BC3 sheets decorated with Li atoms. Their hydrogen storage capacities are determined using density-functional theory in conjunction with a quantum-thermodynamic model that allows to simulate real operating conditions, i.e., finite temperatures and different loading and depletion pressures applied to the adsorbent in the charge-delivery cycles. We show that the capacities of the adsorbed hydrogen phase of Li-decorated BC3 slit pores are larger than those reported recently for graphene and Li-decorated borophene slit pores. On the other hand, the usable volumetric and gravimetric capacities of Li-decorated BC3 slit pores can meet the targets stipulated by the U.S. Department of Energy (DOE) for onboard hydrogen storage at moderate temperatures and loading pressures well below those used in the tanks employed in current technology. In particular, the usable volumetric capacity for pore widths of about 10 {\AA} meets the DOE target at a loading pressure of 6.6 MPa when depleting at ambient pressure. Our results highlight the important role played by the rotational degree of freedom of the H2 molecule in determining the confining potential within the slip pores and their hydrogen storage capacities.

Emergent Atomic Environments in Twisted Bilayer Graphene and Their Use in the Prediction of the Vibrational Properties. (arXiv:2312.12864v1 [cond-mat.mtrl-sci])
Dilara Ickecan, Yunus Emre Okyayli, Erdi Ata Bleda, Dogan Erbahar

While Bernal stacked bilayer graphene bears two distinct atom types in its lattice, there exists no analytical framework addressing the number of atomic environments that emerge in twisted bilayer graphene superlattices. In this work, we have computationally analyzed 120 different twisted bilayer superlattices using descriptor functions to study the emergent local environments. Our study reveals that the number of atoms with unique local environments depend on the superlattice size linearly. Moreover, this linear dependence manifests itself on two distinct lines and this automatically suggests a new classification scheme based on the local environments. As a possible application, the use of local environments in the investigation of vibrational properties is discussed with respect to the existing literature. Molecular dynamics simulations are performed to calculate the phonon density of states of the 120 structures as well as the local phonon density of states of their individual atoms. The similarity of the contributions of local density of states coming from atoms with the same local environment is demonstrated. Local density of states of the atoms with unique local environments of an arbitrary selection of the structures is then used to train a machine learning model. This model is used to predict the phonon spectra of twisted bilayer structures. Performance of the trained model is discussed thoroughly via different selection of training and test sets, and it is shown that the model proves effective in predicting the vibrational properties of any given twisted bilayer structure. The possible applications of the generic method presented which reaches far beyond twisted bilayer graphene is also discussed.

Singular Hall response from a correlated ferromagnetic flat nodal-line semimetal. (arXiv:2312.12889v1 [cond-mat.str-el])
Woohyun Cho, Yoon-Gu Kang, Jaehun Cha, Dong Hyun David Lee, Do Hoon Kiem, Jaewhan Oh, Jongho Park, Changyoung Kim, Yongsoo Yang, Yeong Kwan Kim, Myung Joon Han, Heejun Yang

Topological quantum phases have been largely understood in weakly correlated systems, which have identified various quantum phenomena such as spin Hall effect, protected transport of helical fermions, and topological superconductivity. Robust ferromagnetic order in correlated topological materials particularly attracts attention, as it can provide a versatile platform for novel quantum devices. Here, we report singular Hall response arising from a unique band structure of flat topological nodal lines in combination with electron correlation in an itinerant, van der Waals ferromagnetic semimetal, Fe3GaTe2, with a high Curie temperature of Tc=360 K. High anomalous Hall conductivity violating the conventional scaling, resistivity upturn at low temperature, and a large Sommerfeld coefficient are observed in Fe3GaTe2, which implies heavy fermion features in this ferromagnetic topological material. Our circular dichroism in angle-resolved photoemission spectroscopy and theoretical calculations support the original electronic features in the material. Thus, low-dimensional Fe3GaTe2 with electronic correlation, topology, and room-temperature ferromagnetic order appears to be a promising candidate for robust quantum devices.

Fermi arcs, Landau levels and magnetic response of the nematic Weyl liquid. (arXiv:2312.12920v1 [cond-mat.str-el])
Carlos Naya, Tommaso Bertolini, Johan Carlström

In classes of Weyl semimetals where the symmetry protects nodes with higher than unit charge, the nematic Weyl liquid appears as interactions destroy this underlying symmetry. In the symmetry-broken phase, the multiple-charge nodes are split into objects of unit charge, the position of which in momentum space is determined by the nematic order parameter. We examine the phenomenology of this phase, focusing on topological edge states and Landau levels. We find that the symmetry-broken phase itself, as well as the orientation of the nematic order, are identifiable from the resulting edge states. We also find that the nematic order couples to an in-plane magnetic field, indicating that it can be controlled in situ via an external field. Finally, we provide an estimate for the critical coupling where spontaneous symmetry-breaking occurs for contact interaction.

Effect of molecular rotation and concentration on the adsorption of pentacene molecules on two-dimensional monolayer transition metal dichalcogenides. (arXiv:2312.13025v1 [cond-mat.mtrl-sci])
Edward Black, Juliana Morbec

Heterostructures composed of pentacene (PEN) molecules and transition metal dichalchogenides (TMDs) are promising materials for small, flexible and lightweight photovoltaic devices and various other optoelectronic applications. The effects of changing concentration and orientation of adsorbed pentacene molecules on two-dimensional monolayer substrates of TMDs, namely MoS$_2$, MoSe$_2$, WS$_2$ and WSe$_2$, were investigated using first-principles calculations based on density functional theory. We examined the structural and electronic properties of the corresponding PEN/TMD heterostructures and compared these between differing pentacene concentrations and the orientations of pentacene with respect to the underlying substrate crystal structure. We analyse the band alignment of the heterostructures and demonstrate a concentration-dependent staggered-to-straddling (typeII-I) band gap transition in PEN/MoSe$_2$

BerryEasy: A GPU enabled python package for diagnosis of $n$-th-order and spin-resolved topology in the presence of fields and effects. (arXiv:2312.13051v1 [cond-mat.mtrl-sci])
Alexander C. Tyner

Multiple software packages currently exist for the computation of bulk topological invariants in both idealized tight-binding models and realistic Wannier tight-binding models derived from density functional theory. Currently, only one package, PythTB( is capable of computing nested Wilson loops and spin-resolved Wilson loops. These state-of-the-art techniques are vital for accurate analysis of band topology. In this paper we introduce BerryEasy, a python package which is built to work alongside the PyBinding( software package. By working in tandem with the Pybinding package and harnessing the speed of graphical processing units, topological analysis of supercells in the presence of disorder and impurities is made possible. The BerryEasy package simultaneously accommodates use of realistic tight-binding models developed using Wannier90.

Theory of superconductivity in thin films under an external electric field. (arXiv:2312.13059v1 [cond-mat.supr-con])
Alessio Zaccone, Vladimir M. Fomin

The supercurrent field effect is experimentally realized in various nano-scale devices, based on the superconductivity suppression by external electric fields being effective for confined systems. In spite of intense research, a microscopic theory and explanation of this effect is missing. Here, a microscopic theory of phonon-mediated superconductivity in thin films is presented, which accounts for the effect of quantum confinement on the electronic density of states, on the Fermi energy, and on the topology of allowed states in momentum space. By further accounting for the interplay between quantum confinement, the external static electric field, the Thomas-Fermi screening in the electron-phonon matrix element, and the effect of confinement on the Coulomb repulsion parameter, the theory predicts the critical value of the external electric field as a function of the film thickness, above which superconductivity is suppressed. In particular, this critical value of the electric field is the lower the thinner the film, in agreement with recent experimental observations. Crucially, this effect is predicted by the theory when both Thomas-Fermi screening and the Coulomb pseudopotential are taken into account, along with the respective dependence on thin film thickness. This microscopic theory of the supercurrent field-effect opens up new possibilities for electric-field gated quantum materials.

From noise on the sites to noise on the links: discretizing the conserved Kardar-Parisi-Zhang equation in real space. (arXiv:2312.13065v1 [cond-mat.stat-mech])
Andrea Cavagna, Javier Cristín, Irene Giardina, Mario Veca

Numerical analysis of conserved field dynamics has been generally performed with pseudo spectral methods. Finite differences integration, the common procedure for non-conserved field dynamics, indeed struggles to implement a conservative noise in the discrete spatial domain. In this work, we present a novel method to generate a conservative noise in the finite differences framework, which works for any discrete topology and boundary conditions. We apply it to numerically solve the conserved Kardar-Parisi-Zhang (cKPZ) equation, widely used to describe surface roughening when the number of particles is conserved. Our numerical simulations recover the correct scaling exponents $\alpha$, $\beta$, and $z$ in $d=1$ and in $d=2$. To illustrate the potentiality of the method, we further consider the cKPZ equation on different kinds of non-standard lattices and on the random Euclidean graph. This is the first numerical study of conserved field dynamics on an irregular topology, paving the way to a broad spectrum of possible applications.

An effective field theory of damped ferromagnetic systems. (arXiv:2312.13093v1 [hep-th])
Jingping Li

Using the in-in formalism, we generalize the recently constructed magnetoelastic EFT arXiv:2112.13873 [hep-th] to describe the damping dynamics of ferromagnetic systems at long wavelengths. We find that the standard Gilbert damping term naturally arises as the simplest leading-order symmetry-consistent non-conservative contribution within the in-in framework. The EFT is easily generalized to scenarios with anisotropy and inhomogeneity. In particular, we find the classic Landau-Lifshitz damping term emerges when isotropy is broken by a constant external background field. This provides a first principle explanation for distinguishing the two types of damping dynamics that were originally constructed phenomenologically. Furthermore, the EFT framework could also incorporate intrinsic anisotropy of the material in a straightforward way using the spurion method. For systems with inhomogeneity such as nontrivial spin textures, we find that the leading order derivative correction yields the generalized Gilbert damping equations that were found in condensed matter literature. This shows that the EFT approach enables us to derive the form of higher-derivative-order corrections in a systematic way. Lastly, using the phonon-magnon coupling deduced in the magnetoelastic EFT, we are able to make a prediction for the generic form of the phononic contribution to the damping equation.

Accelerated adiabatic passage of a single electron spin qubit in quantum dots. (arXiv:2312.13135v1 [cond-mat.mes-hall])
Xiao-Fei Liu, Yuta Matsumoto, Takafumi Fujita, Arne Ludwig, Andreas D. Wieck, Akira Oiwa

Adiabatic processes can keep the quantum system in its instantaneous eigenstate, which is robust to noises and dissipation. However, it is limited by sufficiently slow evolution. Here, we experimentally demonstrate the transitionless quantum driving (TLQD) of the shortcuts to adiabaticity (STA) in gate-defined semiconductor quantum dots (QDs) to greatly accelerate the conventional adiabatic passage for the first time. For a given efficiency of quantum state transfer, the acceleration can be more than 2-fold. The dynamic properties also prove that the TLQD can guarantee fast and high-fidelity quantum state transfer. In order to compensate for the diabatic errors caused by dephasing noises, the modified TLQD is proposed and demonstrated in experiment by enlarging the width of the counter-diabatic drivings. The benchmarking shows that the state transfer fidelity of 97.8% can be achieved. This work will greatly promote researches and applications about quantum simulations and adiabatic quantum computation based on the gate-defined QDs.

Non-linear photoconductivity of strongly driven graphene. (arXiv:2312.13217v1 [cond-mat.mes-hall])
Lukas Broers, Ludwig Mathey

We present the non-linear DC photoconductivity of graphene under strong infra-red (IR) radiation. The photoconductivity is obtained as the response to a strong DC electric field, with field strengths outside of the linear-response regime, while the IR radiation is described by a strong AC electric field. The conductivity displays two distinct regimes in which either the DC or the AC field dominates. We explore these regimes and associate them with the dynamics of driven Landau-Zener quenches in the case of a large DC field. In the limit of large AC field, we describe the conductivity in a Floquet picture and compare the results to the closely related Tien-Gordon effect. We present analytical calculations for the non-linear differential photoconductivity, for both regimes based on the corresponding mechanisms. As part of this discussion of the non-equilibrium state of graphene, we present analytical estimates of the conductivity of undriven graphene as a function of temperature and DC bias field strength that show very good agreement with our simulations.

Edge zeros and boundary spinons in topological Mott insulators. (arXiv:2312.13226v1 [cond-mat.str-el])
Niklas Wagner, Daniele Guerci, Andrew J. Millis, Giorgio Sangiovanni

We introduce a real-space slave rotor theory of the physics of topological Mott insulators, using the Kane-Mele-Hubbard model as an example, and use it to show that a topological gap in the Green function zeros corresponds to a gap in the bulk spinon spectrum and that a zero edge mode corresponds to a spinon edge mode. We then consider an interface between a topological Mott insulator and a conventional topological insulator showing how the spinon edge mode of the topological Mott insulator combines with the spin part of the conventional electron topological edge state leaving a non-Fermi liquid edge mode described by a gapless propagating holon and gapped spinon state. Our work demonstrates the physical meaning of Green function zeros and shows that interfaces between conventional and Mott topological insulators are a rich source of new physics.

Extended Baxter relations and QQ-systems for quantum affine algebras. (arXiv:2312.13256v1 [math.QA])
Edward Frenkel, David Hernandez

Generalized Baxter's TQ-relations and the QQ-system are systems of algebraic relations in the category O of representations of the Borel subalgebra of a quantum affine algebra U_q(g^), which we established in our earlier works arXiv:1308.3444 and arXiv:1606.05301. In the present paper, we conjecture a family of analogous relations labeled by elements of the Weyl group W of g, so that the original relations correspond to the identity element. These relations are closely connected to the W-symmetry of q-characters established in arXiv:2211.09779. We prove these relations for all w in W if g has rank two, and we prove the extended TQ-relations if w is a simple reflection. We also generalize our results and conjectures to the shifted quantum affine algebras.

Exact correlations in topological quantum chains. (arXiv:2105.13359v3 [quant-ph] UPDATED)
Nick G. Jones, Ruben Verresen

Although free-fermion systems are considered exactly solvable, they generically do not admit closed expressions for nonlocal quantities such as topological string correlations or entanglement measures. We derive closed expressions for such quantities for a dense subclass of certain classes of topological fermionic wires (classes BDI and AIII). Our results also apply to spin chains called generalised cluster models. While there is a bijection between general models in these classes and Laurent polynomials, restricting to polynomials with degenerate zeros leads to a plethora of exact results: (1) we derive closed expressions for the string correlation functions - the order parameters for the topological phases in these classes; (2) we obtain an exact formula for the characteristic polynomial of the correlation matrix, giving insight into ground state entanglement; (3) the latter implies that the ground state can be described by a matrix product state (MPS) with a finite bond dimension in the thermodynamic limit - an independent and explicit construction for the BDI class is given in a concurrent work [Phys. Rev. Res. 3 (2021), 033265, 26 pages, arXiv:2105.12143]; (4) for BDI models with even integer topological invariant, all non-zero eigenvalues of the transfer matrix are identified as products of zeros and inverse zeros of the aforementioned polynomial. General models in these classes can be obtained by taking limits of the models we analyse, giving a further application of our results. To the best of our knowledge, these results constitute the first application of Day's formula and Gorodetsky's formula for Toeplitz determinants to many-body quantum physics.

Learning Lattice Quantum Field Theories with Equivariant Continuous Flows. (arXiv:2207.00283v3 [hep-lat] UPDATED)
Mathis Gerdes, Pim de Haan, Corrado Rainone, Roberto Bondesan, Miranda C. N. Cheng

We propose a novel machine learning method for sampling from the high-dimensional probability distributions of Lattice Field Theories, which is based on a single neural ODE layer and incorporates the full symmetries of the problem. We test our model on the $\phi^4$ theory, showing that it systematically outperforms previously proposed flow-based methods in sampling efficiency, and the improvement is especially pronounced for larger lattices. Furthermore, we demonstrate that our model can learn a continuous family of theories at once, and the results of learning can be transferred to larger lattices. Such generalizations further accentuate the advantages of machine learning methods.

Magneto-active composites with locally tailored stiffness produced by laser powder bed fusion. (arXiv:2305.02643v2 [] UPDATED)
Kilian Schäfer, Matthias Lutzi, Muhammad Bilal Khan, Lukas Schäfer, Konstantin Skokov, Imants Dirba, Sebastian Bruns, Iman Valizadeh, Oliver Weeger, Claas Hartmann, Mario Kupnik, Esmaeil Adabifiroozjaei, Leopoldo Molina-Luna, Oliver Gutfleisch

Additive manufacturing technologies enable the production of complex and bioinspired shapes using magneto-responsive materials, which find diverse applications in soft robotics. Particularly, the development of composites with controlled gradients in mechanical properties offers new prospects for advancements in magneto-active materials. However, achieving such composites with gradients typically involves complex multi-material printing procedures. In this study, a single-step laser powder bed fusion (LPBF) process is proposed that enables precise local adjustments of the mechanical stiffness within magneto-active composites. By utilizing distinct laser parameters in specific regions of a composite containing thermoplastic polyurethane and atomized magnetic powder derived from hard magnetic Nd-Fe-B, the stiffness of the composite can be modified within the range of 2 to 22 MPa. Various magneto-responsive actuators with locally tailored stiffness are fabricated and their magnetic performance is investigated. The enhanced response exhibited by actuators with locally adjusted mechanical properties in comparison to their homogeneous counterparts with identical geometries is shown. As a demonstration of a biomedical application, a magnetically responsive stent with localized adjustment is presented with the ability to meet specific requirements in terms of geometry and local stiffness based on an individual's anatomy and disease condition. The proposed method presents an approach for creating functionally graded materials using LPBF, not only for magneto-active materials but also for several other structural and functional materials.

Twisted bilayer graphene at charge neutrality: competing orders of SU(4) Dirac fermions. (arXiv:2305.06949v2 [cond-mat.str-el] UPDATED)
Nikolaos Parthenios, Laura Classen

We study possible patterns for spontaneous symmetry breaking in a Dirac fermion model, which is applicable to twisted bilayer graphene at charge neutrality. We show how a chiral SU(4) symmetry emerges and construct the corresponding low-energy model that includes a Fierz-complete set of symmetry-allowed four-fermion interactions. We employ an unbiased renormalization group treatment to identify the critical points that describe transitions into different ordered phases. The resulting phase diagram depends on the number of fermion flavours and we show that the coupling between ordering channels prevents many of the possible mean-field orders from being accessible at relevant, small flavour numbers. We argue that, as a consequence, twisted bilayer graphene is governed by a quantum Hall state or an SU(4) manifold of insulating spin-valley orders with emergent Lorentz symmetry that contains inter-valley coherent, spin Hall, and valley Hall states. We study how SU(4)-breaking perturbations affect the accessibility and can additionally stabilize symmetry-broken (semi-)metallic states.

In-situ spontaneous emission control of MoSe$_2$-WSe$_2$ interlayer excitons with near-unity quantum yield. (arXiv:2306.15101v2 [cond-mat.mtrl-sci] UPDATED)
Bo Han, Chirag Chandrakant Palekar, Sven Stephan, Frederik Lohof, Victor Nikolaevich Mitryakhin, Jens-Christian Drawer, Alexander Steinhoff, Lukas Lackner, Martin Silies, Bárbara Rosa, Martin Esmann, Falk Eilenberger, Christopher Gies, Stephan Reitzenstein, Christian Schneider

Optical resonators are a powerful platform to control the spontaneous emission dynamics of excitons in solid-state nanostructures. Here, we study a MoSe$_2$-WSe$_2$ van-der-Waals heterostructure that is integrated in a widely tunable open optical microcavity to gain insights into fundamental optical properties of the emergent interlayer charge-transfer excitons. First, we utilize an ultra-low quality factor open planar vertical cavity and investigate the modification of the excitonic lifetime as on- and off-resonant conditions are met with consecutive longitudinal modes. Time-resolved photoluminescence measurements reveal that the interlayer exciton lifetime can thus be periodically tuned with an amplitude of 110 ps. The resulting oscillations of the interlayer exciton lifetime allows us to extract a 0.5 ns free-space radiative lifetime and a quantum efficiency as high as 81 \%. We subsequently engineer the local density of optical states by introducing a spatially confined and fully spectrally tunable Tamm-plasmon resonance. The dramatic redistribution of the local optical modes in this setting allows us to encounter a profound inhibition of spontaneous emission of the interlayer excitons by a factor of 3.2. We expect that specifically engineering the inhibition of radiation from moir\'e excitons is a powerful tool to steer their thermalization, and eventually their condensation into coherent condensate phases.

Competition between fractional quantum Hall liquid and electron solid phases in the Landau levels of multilayer graphene. (arXiv:2307.14519v2 [cond-mat.mes-hall] UPDATED)
Rakesh K. Dora, Ajit C. Balram

We study the competition between the electron liquid and solid phases, such as Wigner crystal and bubbles, in partially filled Landau levels (LLs) of multilayer graphene. Graphene systems offer a versatile platform for controlling band dispersion by varying the number of its stacked layers. The band dispersion determines the LL wave functions, and consequently, the LL-projected Coulomb interaction in graphene and its multilayers is different from that in conventional semiconductors like GaAs. As a result, the energies of the liquid and solid phases are different in the different LLs of multilayer graphene, leading to an alternative phase diagram for the stability of these phases, which we work out. The phase diagram of competing solid and liquid phases in the LLs of monolayer graphene has been studied previously. Here, we primarily consider $AB{-}$ or Bernal$-$stacked bilayer graphene (BLG) and $ABC{-}$stacked trilayer graphene (TLG) and focus on the Laughlin fractions. We determine the cohesive energy of the solid phase using the Hartree-Fock approximation, and the energy of the Laughlin liquid is computed analytically via the plasma sum rules. We find that at the Laughlin fillings, the electron liquid phase has the lowest energy among the phases considered in the $\mathcal{N}{=}0, 1, 2$ LLs of BLG, as well as in the $\mathcal{N}{=}3, 4$ LLs of TLG, while in the $\mathcal{N}{>}2$ LLs of BLG and $\mathcal{N}{>}4$ LLs of TLG, the solid phases are more favorable. We also discuss the effect of impurities on the above-mentioned phase diagram.

Non-Fermi Liquid Behavior of the $t$-$J$ Model in the Strange Metal Phase: $U(1)$ Gauge Theory Consistent with Local Constraints. (arXiv:2308.03074v3 [cond-mat.str-el] UPDATED)
Long Liang, Yue Yu, Xi Luo

We use the Becchi-Rouet-Stora-Tyutin (BRST) method to quantize the $t$-$J$ model in the $U(1)$ gauge slave boson representation. While the temporal component of the gauge field plays a role of a Lagrange multiplier to enforce the no double occupancy constraint, the spatial components do that to enforce the vanishing counterflow constraints of the spinon and holon currents. These constraints on the ordered states of the $t$-$J$ model belong to Dirac's second-class constraints. The BRST quantization theory which is consistent with the second-class constraints was not built in literature. We successfully develop such a BRST quantization theory in which the gauge invariance is guaranteed and the redundant gauge degrees of freedom are removed by proper gauge fixing conditions while the no double occupancy and vanishing counterflow constraints are exactly retained. Furthermore, the gauge fixing conditions endow the gauge field with dynamics. This turns the strongly correlated electron model into a weakly coupled slave boson model, most of whose physical observable can be calculated by the conventional quantum many-body perturbation theory. We focus on the properties of the strange metal phase in the $t$-$J$ model. The electron momentum distribution and the spectral function are calculated, and their non-Fermi liquid behaviors agree with the angle resolved photoemission spectroscopy measurements for the cuprate materials. We also study the responses of the strange metal state to the external electromagnetic fields. The non-Fermi liquid anomalies observed in cuprates are captured by our calculations. Especially, we find that the Hall resistivity decreases as temperature raises and the sign of the Hall resistivity varies from negative to positive when the dopant concentration varies from the optimal doping one to underdoping one for the temperature $T>T^*$.

Orbital Chern Insulator at $\nu=-2$ in Twisted MoTe$_{2}$. (arXiv:2308.11454v2 [cond-mat.str-el] UPDATED)
Feng-Ren Fan, Cong Xiao, Wang Yao

In twisted MoTe$_{2}$, latest transport measurement has reported observation of quantum anomalous Hall effect at hole filling $\nu=-1$, which undergoes a topological phase transition to a trivial ferromagnet as layer hybridization gets suppressed by interlayer bias $D$. Here we show that this underlies the existence of an orbital Chern insulating state with gate ($D$) switchable sign in an antiferromagtic spin background at hole filling $\nu=-2$. From momentum-space Hartree Fock calculations, we find this state has a topological phase diagram complementary to that of the $\nu=-1$ one: by sweeping $D$ from negative to positive, the Chern number of this $\nu=-2$ state can be switched between $+1$, $0$, and $-1$, accompanied by a sign change of a sizable orbital magnetization. In range of $D$ where this antiferronagnet is the ground state, the orbital magnetization allows magnetic field initialization of the spin antiferromagnetic order and the Chern number.

How heat propagates in liquid $^3$He. (arXiv:2309.00502v2 [cond-mat.stat-mech] UPDATED)
Kamran Behnia, Kostya Trachenko

In Landau's Fermi liquid picture, transport is governed by scattering between quasi-particles. The normal liquid $^3$He conforms to this picture but only at very low temperature. Here, we observe that the deviation from the standard behavior is concomitant with the fermion-fermion scattering time falling below the Planckian time, $\frac{\hbar}{k_{\rm B}T}$. We also observe that thermal diffusivity of this quantum liquid is bounded by a minimum set by fundamental physical constants, similarly to what was observed in classical liquids earlier. This points to collective excitations (a sound mode) as carriers of heat. We propose that this mode has a wavevector of 2$k_F$ and a mean free path equal to the de Broglie thermal length. This would provide an additional conducting channel with a $T^{1/2}$ temperature dependence, matching what is observed by experiments. Within a margin of 10\%, the experimental data from 0.007 K to 3 K can be accounted for if thermal conductivity is the sum of contributions from quasiparticles and sound: $\kappa=\kappa_{qp}+\kappa_s$; $\kappa_{qp}\propto T^{-1}$; $\kappa_s\propto T^{1/2}$.

Topological superconductivity mediated by magnons of helical magnetic states. (arXiv:2309.07211v2 [cond-mat.supr-con] UPDATED)
Kristian Mæland, Sara Abnar, Jacob Benestad, Asle Sudbø

We recently showed that spin fluctuations of noncoplanar magnetic states can induce topological superconductivity in an adjacent normal metal [M{\ae}land et al., Phys. Rev. Lett. 130, 156002 (2023)]. The noncolinear nature of the spins was found to be essential for this result, while the necessity of noncoplanar spins was unclear. In this paper we show that magnons in coplanar, noncolinear magnetic states can mediate topological superconductivity in a normal metal. Two models of the Dzyaloshinskii-Moriya interaction are studied to illustrate the need for a sufficiently complicated Hamiltonian describing the magnetic insulator. The Hamiltonian, in particular the specific form of the Dzyaloshinskii-Moriya interaction, affects the magnons and by extension the effective electron-electron interaction in the normal metal. Symmetry arguments are applied to complement this discussion. We solve a linearized gap equation in the case of weak-coupling superconductivity. The result is a time-reversal-symmetric topological superconductor, as confirmed by calculating the topological invariant. In analogy with magnon-mediated superconductivity from antiferromagnets, Umklapp scattering enhances the critical temperature of superconductivity for certain Fermi momenta.

On the dynamical stability of copper-doped lead apatite. (arXiv:2309.11541v2 [cond-mat.supr-con] UPDATED)
Sun-Woo Kim, Kang Wang, Siyu Chen, Lewis J. Conway, G. Lucian Pascut, Ion Errea, Chris J. Pickard, Bartomeu Monserrat

The recent claim of room temperature superconductivity in a copper-doped lead apatite compound, called LK-99, has sparked remarkable interest and controversy. Subsequent experiments have largely failed to reproduce the claimed superconductivity, while theoretical works have identified multiple key features including strong electronic correlation, structural instabilities, and dopability constraints. A puzzling claim of several recent theoretical studies is that both parent and copper-doped lead apatite structures are dynamically unstable at the harmonic level, questioning decades of experimental reports of the parent compound structures and the recently proposed copper-doped structures. In this work, we demonstrate that both parent and copper-doped lead apatite structures are dynamically stable at room temperature. Anharmonic phonon-phonon interactions play a key role in stabilizing some copper-doped phases, while most phases are largely stable even at the harmonic level. We also show that dynamical stability depends on both volume and correlation strength, suggesting controllable ways of exploring the copper-doped lead apatite structural phase diagram. Our results fully reconcile the theoretical description of the structures of both parent and copper-doped lead apatite with experiment.

pyCOFBuilder: A python package for automated creation of Covalent Organic Framework models based on the reticular approach. (arXiv:2310.14822v2 [cond-mat.mtrl-sci] UPDATED)
Felipe Lopes Oliveira, Pierre Mothé Esteves

Covalent Organic Frameworks (COFs) have gained significant popularity in recent years due to their unique ability to provide a high surface area and customizable pore geometry and chemistry. These traits make COFs a highly promising choice for a range of applications. However, with their vast potential structures, exploring COFs experimentally can be challenging and time-consuming, yet it remains an attractive avenue for computational high-throughput studies. However, generating COF structures can be a time-consuming and challenging task. To address this challenge, here we introduce the pyCOFBuilder, an open-source Python package designed to facilitate the generation of COF structures for computational studies. The pyCOFBuilder software provides an easy-to-use set of functionalities to generate COF structures following the reticular approach. In this paper, we describe the implementation, main features, and capabilities of the pyCOFBuilder demonstrating its utility for generating COF structures with varying topologies and chemical properties. pyCOFBuilder is freely available on GitHub at

Two-dimensional symmetry-protected topological phases and transitions in open quantum systems. (arXiv:2311.12619v3 [quant-ph] UPDATED)
Yuxuan Guo, Yuto Ashida

We investigate the influence of local decoherence on a symmetry-protected topological (SPT) phase of the two-dimensional (2D) cluster state. Mapping the 2D cluster state under decoherence to a classical spin model, we show a topological phase transition of a $\mathbb{Z}_2^{(0)}\times\mathbb{Z}_{2}^{(1)}$ SPT phase into the trivial phase occurring at a finite decoherence strength. To characterize the phase transition, we employ three distinct diagnostic methods, namely, the relative entropy between two decohered SPT states with different topological edge states, the strange correlation function of $\mathbb{Z}_2^{(1)}$ charge, and the multipartite negativity of the mixed state on a disk. All the diagnostics can be obtained as certain thermodynamic quantities in the corresponding classical model, and the results of three diagnostic tests are consistent with each other. Given that the 2D cluster state possesses universal computational capabilities in the context of measurement-based quantum computation, the topological phase transition found here can also be interpreted as a transition in the computational power.

State Diagrams to determine Tree Tensor Network Operators. (arXiv:2311.13433v2 [quant-ph] UPDATED)
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 $3$.

A Novel Interface Database of Graphene Nanoribbon from Density Functional Theory. (arXiv:2311.18203v2 [cond-mat.mtrl-sci] UPDATED)
Ao Wu, Jiangxue Huang, Qijun Huang, Jin He, Hao Wang, Sheng Chang

Interfaces play a crucial role in determining the overall performance and functionality of electronic devices and systems. Driven by the data science, machine learning (ML) reveals excellent guidance for material selection and device design, in which an advanced database is crucial for training models with state-of-the-art (SOTA) precision. However, a systematic database of interfaces is still in its infancy due to the difficulties in collecting raw data in experiment and the expensive first-principles computational cost in density functional theory (DFT). In this paper, we construct ample interface structures of graphene nanoribbons (GNR), whose interfacial morphology can be precisely fabricated based on specific molecular precursors. The GNR interfaces serve as promising candidates since their bandgaps can be modulated. Their physical properties including energy bands and density of states (DOS) maps are obtained under reasonable calculation parameters. This database can provide theoretical guidance for the design of electronic devices and accelerate the ML study of various physical quantities.

Static magnetic order with strong quantum fluctuations in spin-1/2 honeycomb magnet Na2Co2TeO6. (arXiv:2312.06284v2 [cond-mat.str-el] UPDATED)
Gaoting Lin, Jinlong Jiao, Xiyang Li, Mingfang Shu, Oksana Zaharko, Toni Shiroka, Tao Hong, Alexander I. Kolesnikov, Guochu Deng, Sarah Dunsiger, Haidong Zhou, Tian Shang, Jie Ma

Kitaev interactions, arising from the interplay of frustration and bond anisotropy, can lead to strong quantum fluctuations and, in an ideal case, to a quantum-spin-liquid state. However, in many nonideal materials, spurious non-Kitaev interactions typically promote a zigzag antiferromagnetic order in the d-orbital transition metal compounds. By combining neutron scattering with muon-spin rotation and relaxation techniques, we provide new insights into the exotic properties of Na2Co2TeO6, a candidate Kitaev material. Below TN, the zero-field muon-spin relaxation rate becomes almost constant (at 0.45 us-1). We attribute this temperature-independent muon-spin relaxation rate to the strong quantum fluctuations, as well as to the frustrated Kitaev interactions. As the magnetic field increases, neutron scattering data indicate a much broader spin-wave-excitation gap at the K-point. Therefore, quantum fluctuations seem not only robust, but are even enhanced by the applied magnetic field. Our findings provide valuable hints for understanding the onset of the quantum-spin-liquid state in Kitaev materials.

Realization of A Superconducting FeTe/Bi$_2$Te$_3$ Heterostructure. (arXiv:2312.10408v2 [cond-mat.supr-con] UPDATED)
Zhihao He, Tin Seng Manfred Ho, Rolf Lortz, Iam Keong Sou

Before this study, we observed an intriguing occurrence of two-dimensional (2D) superconductivity in two heterostructures, Bi$_2$Te$_3$/FeTe and Sb$_2$Te$_3$/FeTe, which consist of a topological insulator (TI) on top and FeTe on the bottom. The objective of this study was to create an inverted version of the Bi$_2$Te$_3$/FeTe (BT-FT) heterostructure, called FeTe/Bi$_2$Te$_3$ (FT-BT). Through in-situ reflection high-energy electron diffraction (RHEED), high-resolution x-ray diffraction (HRXRD) profiling and cross-sectional scanning transmission electron microscopy (STEM) imaging studies, it was found that at a relatively high growth temperature, FeTe grown on Bi$_2$Te$_3$ led to the extraction of Te from the Bi$_2$Te$_3$ layer, resulting the formation of Bi$_4$Te$_3$ as the bottom layer. This is attributed to the more negative formation energy of FeTe compared to that of Bi$_2$Te$_3$. In addition, a nearly ideal heterostructure of FeTe/Bi$_2$Te$_3$ was successfully fabricated at a lower growth temperature of FeTe with certain Fe and Te cell temperatures. This heterostructure exhibits superconductivity at approximately 12K. These studies present a new approach to realizing the Bi$_4$Te$_3$ component of the Bi-Te system, which could potentially be used to generate other components within the Bi-Te system. The realization of the FeTe/Bi$_2$Te$_3$ inverted heterostructure creates a platform for configuring structures with multiple interfaces between Bi$_2$Te$_3$ and FeTe. This is expected to enhance superconductivity due to its more three-dimensional nature.

Found 9 papers in prb
Date of feed: Thu, 21 Dec 2023 04:16:56 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)

Giant conductivity anisotropy in cubic ${\mathrm{CuCr}}_{2}{\mathrm{Te}}_{3}\mathrm{I}$ and semiconducting behavior in ${\mathrm{CuCr}}_{2}{\mathrm{S}}_{3}\mathrm{Cl}$ and ${\mathrm{CuCr}}_{2}{\mathrm{Se}}_{3}\mathrm{Br}$
David J. Singh
Author(s): David J. Singh

Spinel structure ${\mathrm{CuCr}}_{2}{X}_{4}$ where $X$ is a chalcogen are ferromagnetic metals with Curie temperatures at or above room temperature. Experiments show that these compounds can be alloyed with halogens while preserving the ferromagnetic ordering. This alloying changes the carrier conc…

[Phys. Rev. B 108, 214422] Published Wed Dec 20, 2023

sp- and $d$-band effects on secondary low-energy electron generation
V. Desbuis, D. Lacour, C. Tiusan, W. Weber, and M. Hehn
Author(s): V. Desbuis, D. Lacour, C. Tiusan, W. Weber, and M. Hehn

Ballistic hot electrons are extracted from a magnetic tunnel junction and injected into a metallic base with energies ranging from 0.65 to 2.8 eV. The energy and wave vector analysis made by a low height Si/Cu Schottky barrier allows one to disentangle the different contributions to the scattering. …

[Phys. Rev. B 108, 214424] Published Wed Dec 20, 2023

Unconventional photoinduced charge density wave dynamics in $2H\text{−}{\mathrm{NbSe}}_{2}$
R. Venturini, A. Sarkar, P. Sutar, Z. Jagličić, Y. Vaskivskyi, E. Goreshnik, D. Mihailovic, and T. Mertelj
Author(s): R. Venturini, A. Sarkar, P. Sutar, Z. Jagličić, Y. Vaskivskyi, E. Goreshnik, D. Mihailovic, and T. Mertelj

Using transient optical spectroscopy, the authors investigate ultrafast optical suppression and recovery of the charge density wave (CDW) in 2H-NbSe2, a layered material where CDW and superconductivity coexist. The suppression is marked by the absence of coherent amplitude mode oscillations and a relatively slow, picosecond timescale, different from most typical CDW materials. The suppression of the CDW is only weakly nonthermal and is characterized by an excitation of a large number of phonon degrees of freedom. The recovery of the CDW phase is dominated by slow phonon diffusion.

[Phys. Rev. B 108, 235160] Published Wed Dec 20, 2023

Accurate and efficient treatment of spin-orbit coupling via second variation employing local orbitals
Cecilia Vona, Sven Lubeck, Hannah Kleine, Andris Gulans, and Claudia Draxl
Author(s): Cecilia Vona, Sven Lubeck, Hannah Kleine, Andris Gulans, and Claudia Draxl

A method is presented that allows for efficient evaluation of spin-orbit coupling (SOC) in density-functional-theory calculations. In the so-called second-variational scheme, where Kohn-Sham functions obtained in a scalar-relativistic calculation are employed as a basis for the spin-orbit-coupled pr…

[Phys. Rev. B 108, 235161] Published Wed Dec 20, 2023

Topological information device operating at the Landauer limit
A. Mert Bozkurt, Alexander Brinkman, and İnanç Adagideli
Author(s): A. Mert Bozkurt, Alexander Brinkman, and İnanç Adagideli

We propose and theoretically investigate a novel Maxwell's demon implementation based on the spin-momentum locking property of topological matter. We use nuclear spins as a memory resource which provides the advantage of scalability. We show that this topological information device can ideally opera…

[Phys. Rev. B 108, 235428] Published Wed Dec 20, 2023

Impact of hydrostatic pressure, nonstoichiometry, and doping on trimeron lattice excitations in magnetite during axis switching
T. Kołodziej, J. Piętosa, R. Puźniak, A. Wiśniewski, G. Król, Z. Kąkol, I. Biało, Z. Tarnawski, M. Ślęzak, K. Podgórska, J. Niewolski, M. A. Gala, A. Kozłowski, J. M. Honig, and W. Tabiś
Author(s): T. Kołodziej, J. Piętosa, R. Puźniak, A. Wiśniewski, G. Król, Z. Kąkol, I. Biało, Z. Tarnawski, M. Ślęzak, K. Podgórska, J. Niewolski, M. A. Gala, A. Kozłowski, J. M. Honig, and W. Tabiś

Trimeron lattice excitations in single crystalline magnetite, in the form of $c$ axis switching (i.e., the reorganization of the lattice caused by an external magnetic field) at temperatures below the Verwey temperature ${T}_{\mathrm{V}}$ are observed by magnetization experiments. These excitations …

[Phys. Rev. B 108, 245148] Published Wed Dec 20, 2023

Polar discontinuities and interfacial electronic properties of ${\mathrm{Bi}}_{2}{\mathrm{O}}_{2}\mathrm{Se}$ on ${\mathrm{SrTiO}}_{3}$
Ziye Zhu, Jingshan Qi, Xiaorui Zheng, Xiao Lin, and Wenbin Li
Author(s): Ziye Zhu, Jingshan Qi, Xiaorui Zheng, Xiao Lin, and Wenbin Li

The layered oxychalcogenide semiconductor ${\mathrm{Bi}}_{2}{\mathrm{O}}_{2}\mathrm{Se}$ (BOS) hosts a multitude of unusual properties including high electron mobility. Owing to similar crystal symmetry and lattice constants, the perovskite oxide ${\mathrm{SrTiO}}_{3}$ (STO) has been demonstrated to…

[Phys. Rev. B 108, 245304] Published Wed Dec 20, 2023

Density functional theory study of the structural and electronic properties of single and double acceptor dopants in $M{X}_{2}$ monolayers
Yuqiang Gao and Paul J. Kelly
Author(s): Yuqiang Gao and Paul J. Kelly

Density functional theory calculations are used to systematically investigate the structural and electronic properties of $M{X}_{2}$ transition metal dichalcogenide monolayers with $M$ = Cr, Mo, W and $X$ = S, Se, Te that are doped with single (V, Nb, Ta) and double (Ti, Zr, Hf) acceptor dopants on …

[Phys. Rev. B 108, 245421] Published Wed Dec 20, 2023

Robust topological edge states induced by latent mirror symmetry
Li-Yang Zheng, Yu-Fan Li, Jin Zhang, and Yongsheng Huang
Author(s): Li-Yang Zheng, Yu-Fan Li, Jin Zhang, and Yongsheng Huang

In recent years, topology has offered an elegant degree of freedom (DOF) for light and sound manipulation. There exists persistent effort to explore the origin of topological phases based on symmetry, while it becomes rather challenging in complex networks or multiple DOF systems where geometric sym…

[Phys. Rev. B 108, L220303] Published Wed Dec 20, 2023

Found 1 papers in prl
Date of feed: Thu, 21 Dec 2023 04:16:54 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)

Complete Hilbert-Space Ergodicity in Quantum Dynamics of Generalized Fibonacci Drives
Saúl Pilatowsky-Cameo, Ceren B. Dag, Wen Wei Ho, and Soonwon Choi
Author(s): Saúl Pilatowsky-Cameo, Ceren B. Dag, Wen Wei Ho, and Soonwon Choi

Ergodicity of quantum dynamics is often defined through statistical properties of energy eigenstates, as exemplified by Berry’s conjecture in single-particle quantum chaos and the eigenstate thermalization hypothesis in many-body settings. In this work, we investigate whether quantum systems can exh…

[Phys. Rev. Lett. 131, 250401] Published Wed Dec 20, 2023

Found 1 papers in prx
Date of feed: Thu, 21 Dec 2023 04:16:55 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)

Measuring Oscillations with a Million Atmospheric Neutrinos
C. A. Argüelles, P. Fernández, I. Martínez-Soler, and M. Jin (靳淼辰)
Author(s): C. A. Argüelles, P. Fernández, I. Martínez-Soler, and M. Jin (靳淼辰)

The combined analysis of present and upcoming atmospheric-neutrino experiments may lead to the solution of outstanding puzzles in neutrino physics.

[Phys. Rev. X 13, 041055] Published Wed Dec 20, 2023

Found 2 papers in pr_res
Date of feed: Thu, 21 Dec 2023 04:16:54 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)

Visualizing the localized electrons of a kagome flat band
Caiyun Chen, Jiangchang Zheng, Ruopeng Yu, Soumya Sankar, Kam Tuen Law, Hoi Chun Po, and Berthold Jäck
Author(s): Caiyun Chen, Jiangchang Zheng, Ruopeng Yu, Soumya Sankar, Kam Tuen Law, Hoi Chun Po, and Berthold Jäck

Destructive interference between electron wavefunctions on the two-dimensional kagome lattice induces an electronic flat band, which could host a variety of interesting quantum states. Key to realize these proposals is to demonstrate the real-space localization of kagome flat-band electrons. The ext…

[Phys. Rev. Research 5, 043269] Published Wed Dec 20, 2023

Determination of the nearest-neighbor interaction in $\mathrm{V}{\mathrm{O}}_{2}$ via fractal dimension analysis
Jacob Holder, Daniel Kazenwadel, Peter Nielaba, and Peter Baum
Author(s): Jacob Holder, Daniel Kazenwadel, Peter Nielaba, and Peter Baum

The Ising model is one of the simplest and most well-established concepts to simulate phase transformations in complex materials. However, its most central constant, the interaction strength $\mathbit{J}$ between two nearest neighbors, is hard to obtain. Here we show how this basic constant can be d…

[Phys. Rev. Research 5, 043272] Published Wed Dec 20, 2023

Found 1 papers in nat-comm

Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Extendable piezo/ferroelectricity in nonstoichiometric 2D transition metal dichalcogenides
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Found 4 papers in comm-phys

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Synthesizing 2h/e2 resistance plateau at the first Landau level confined in a quantum point contact
Yoshiro Hirayama

Communications Physics, Published online: 20 December 2023; doi:10.1038/s42005-023-01491-8

In the quantum Hall regime, electrical current flows along the edges in a chiral fashion and they determine the Hall resistance plateaus. This work reports on experiments on fractional and integer quantum Hall edge channel mixing in a quantum point contact, which lead to unexpectedly anomalous resistance plateaus, shedding light onto the edge reconstruction and equilibration processes.

Efficiency limit of transition metal dichalcogenide solar cells
Eric Pop

Communications Physics, Published online: 20 December 2023; doi:10.1038/s42005-023-01447-y

Transition metal dichalcogenide-based photovoltaics offer the prospect of increased specific power compared to incumbent solar technologies but there are engineering challenges that come with integrating these materials into high-efficiency devices. Here, the authors develop a model to describe the relationship between material quality and the performance limits of single junction solar cells built with various transition metal dichalcogenides.

Selectable diffusion direction with topologically protected edge modes
Hiroya Tanaka

Communications Physics, Published online: 20 December 2023; doi:10.1038/s42005-023-01490-9

Quantum-inspired thermal diffusion systems have been realized the thermal localization and design of robust thermal decay by topological methodology as well as wave systems. As a further development, this paper demonstrates that initial temperature distributions for topological edge modes control the diffusion direction in a honeycomb-shaped periodic structure.

Anomalous non-Hermitian skin effect: topological inequivalence of skin modes versus point gap
Wu-Ming Liu

Communications Physics, Published online: 19 December 2023; doi:10.1038/s42005-023-01487-4

Non-Hermitian skin effect, as an important consequence of a non-Hermitian topological system, has recently attracted great attention. This paper reports an anomalous non-Hermitian skin effect, where the correspondence between skin modes and the non-zero winding number defined within point gaps can be broken, enabling further understanding of the non-Bloch band theory in the non-Hermitian field.