We investigate the effects of an in-plane magnetic field on the weak antilocalization signature of near-surface quantum wells lacking bulk and inversion symmetry. The measured magnetoconductivity, which is conductivity as a function of the out-of-plane magnetic field, exhibits a strong anisotropy with respect to the direction of the in-plane magnetic field. The twofold symmetry of the observed magnetoanisotropy originates from the competition between Rashba and Dresselhaus spin-orbit couplings. The high sensitivity of the weak antilocalization to the spin texture produced by the combined Zeeman and spin-orbit fields results in very large anisotropy ratios, reaching 100%. Using a semiclassical universal model in quantitative agreement with the experimental data, we uniquely determine the values of the Dresselhaus and Rashba parameters as well as the effective in-plane g-factor of the electrons. Understanding these parameters provides prospects for different applications ranging from spintronics to topological quantum computing.

We investigate the quench dynamics of interacting bosons on a two-leg ladder in the presence of a uniform Abelian gauge field. The model hosts a variety of emergent quantum phases, and we focus on the superfluid biased-ladder phase breaking the $Z_2$ symmetry of two legs. We observe an asymmetric spreading of vortex current and particle density, i.e., the vortices propagate ballistically on the right and dissolve during the propagation on the left, indicating spontaneous breaking of the spatial inversion symmetry. By decreasing the repulsion strength, it is found that the ballistic propagating vortices are more robust than the dissolving ones on the other side.

Reservoir engineering is a powerful approach for using controlled driven-dissipative dynamics to prepare target quantum states and phases. In this work, we study a paradigmatic model that can realize a Mott insulator of photons in its steady state. We show that, while in some regimes its steady state approximates a Mott-insulating ground state, this phase can become unstable through a nonequilibrium transition towards a coherent yet nonclassical limit-cycle phase, driven by doublon excitations. This instability is completely distinct from the ground-state Mott-insulator to superfluid transition. This difference has dramatic observable consequences and leads to an intrinsic fragility of the steady-state Mott phase: a fast pump compared to losses is required to sustain the phase, but also determines a small critical hopping. We identify unique features of the steady-state Mott phase and its instability that distinguish them from their ground-state counterpart and can be measured in experiments.

The Fermi-Hubbard model is one of the central paradigms in the physics of strongly correlated quantum many-body systems. Here we propose a quantum circuit algorithm based on the ${\mathrm{Z}}_2$ lattice gauge theory (LGT) representation of the one-dimensional Fermi-Hubbard model, which is suitable for implementation on current NISQ quantum computers. Within the LGT description there is an extensive number of local conserved quantities commuting with the Hamiltonian. We show how these conservation laws can be used to implement an efficient error-mitigation scheme. The latter is based on a postselection of states for noisy quantum simulators. While the LGT description requires a deeper quantum-circuit compared to a Jordan-Wigner (JW) based approach, remarkably, we find that our error-correction protocol leads to results being on par with a standard JW implementation on noisy quantum simulators.

Recently, nonreciprocal two-dimensional unitary scattering networks have gained considerable interest due to the possibility of obtaining robust edge wave propagation in their anomalous topological insulating phase. However, zero-dimensional states in such networks have been left uncharted. Here, we demonstrate the existence of disclination states in nonreciprocal topological scattering networks. The disclination states can nucleate in every gap of the anomalous phase if a disclination round-trip resonance condition is met, and are carried over to the Chern phase unless the band gap closes. By comparing Chern and anomalous disclination states, we show that only the latter are remarkably robust to random quasienergy fluctuations. Anomalous topological chiral edge states and disclinations can be coupled together to form intriguing disclination bound states in the continuum (BICs) in anomalous topological insulators, a different form of nonreciprocal cavities associated with an extreme confinement and lifetime. Our work broadens the applications of disclination states to microwave, acoustic, or optical scattering networks, with new possibilities in chiral topological lasing, robust nonreciprocal energy squeezing, and switchable lasing and antilasing behavior.

Topological quantum materials have significant potential for application as anode materials due to their intrinsically high electronic conductivity against perturbation from defects or impurities. In this work, we utilize a combination of a swarm-intelligence structure search method and first-principles calculations to predict the global minimum of a BeN monolayer, suggesting it as a promising nodal-line semimetal anode for Li-ion batteries. BeN anode demonstrates a substantial specific capacity of 3489 mAh/g and a low average open-circuit voltage of 0.15 V, resulting in an ultrahigh energy density of 9681 mWh/g (referenced to the standard hydrogen electrode potential). This energy density represents the highest among all two-dimensional (2D) topological quantum anodes and surpasses that of most currently known 2D anode materials for Li-ion batteries. Furthermore, the formation of a vacancy in the BeN monolayer induces a unique “self-doping” effect that promotes high electronic conductivity. Additionally, the BeN monolayer exhibits a diffusion energy barrier of 0.30 eV for Li-ion migration, a small-scale area expansion of 0.96% during the process of lithiation, and excellent wettability with the contacted electrolytes.

The topology of the photonic bath shows excellent potential to engineer the intriguing interaction properties between light and matter. Here, we study the dielectric resonator array with a zigzag geometry, an analogy of the Su-Schrieffer-Heeger model equipped with peculiar freedom to manipulate the nearest-neighbor coupling strength by the internal interaction. A staggered coupling strength of $s$-type pillar modes is experimentally achieved via the photonic spin-orbit coupling by employing the zigzag dielectric resonator chain. As a result, we observe that the robust edge states of the zigzag chains manifest themselves with linear polarization for an even number of dielectric resonators but elliptical polarization for an odd number. In addition, by coupling magnons to the topological waveguide, we observe resonant magnon–magnon–edge-state coupling, whose coupling strength is topologically protected. More broadly, our work shows that topological waveguide-QED systems may provide the potential for synthesis and study of many-body states with attractive long-range interaction.

Multipolar Kondo systems offer unprecedented opportunities to design astonishing quantum phases and functionalities beyond spin-only descriptions. A model material platform of this kind is the cubic heavy fermion system $\mathrm{Pr}{T}_2{\mathrm{Al}}_{20}$ $(T=\mathrm{Ti}, \mathrm{V})$, which hosts a nonmagnetic crystal-electric-field ground state and substantial Kondo entanglement of the local quadrupolar and octopolar moments with the conduction electron sea. Here, we explore the magnetoresistance (MR) and Hall effect of ${\mathrm{PrTi}}_2{\mathrm{Al}}_{20}$, which develops ferroquadrupolar (FQ) order below $T_Q\sim 2$ K, and compare their behavior with that of the MR and Hall effect of the non-$4f$ analog, ${\mathrm{LaTi}}_2{\mathrm{Al}}_{20}$. In the FQ ordered phase, ${\mathrm{PrTi}}_2{\mathrm{Al}}_{20}$ displays extremely large magnetoresistance (XMR) of $\sim {10}^3\%$. The unsaturated, quasilinear field $\left(B\right)$ dependence of the XMR violates Kohler's scaling and defies description based on carrier compensation alone. By comparing the MR and the Hall effect observed in ${\mathrm{PrTi}}_2{\mathrm{Al}}_{20}$ and ${\mathrm{LaTi}}_2{\mathrm{Al}}_{20}$, we conclude that the open-orbit topology on the electron-type Fermi surface sheet is key for the observed XMR. The low-temperature MR and the Hall resistivity in ${\mathrm{PrTi}}_2{\mathrm{Al}}_{20}$ display pronounced anisotropy in the [111] and [001] magnetic fields, which is absent in ${\mathrm{LaTi}}_2{\mathrm{Al}}_{20}$, suggesting that the transport anisotropy ties in with the anisotropic magnetic field response of the quadrupolar order parameter.

Light-matter interaction and understanding the fundamental physics behind is essential for emerging quantum technologies. Solid-state devices may explore new regimes where coupling strengths are “ultrastrong”, i.e., comparable to the energies of the subsystems. New exotic phenomena occur the common root of many of them being the fact that the entangled vacuum contains virtual photons. They herald the lack of conservation of the number of excitations which is the witness of ultrastrong coupling breaking the U(1) symmetry. Despite more than a decade of research, the detection of ground-state virtual photons still awaits demonstration. In this work, we recognize the “conspiring” set of experimental challenges and show how to overcome them, thus providing a solution to this long-standing problem. We find that combining a superinductor-based unconventional “light fluxonium” qudit and coherent control yields a highly efficient, faithful, and selective conversion of virtual photons into real ones. This enables their detection with resources available to present-day quantum technologies.

Using state-of-the-art quantum Monte Carlo (QMC) methods, we study straintronic properties of a single ${\mathrm{MoS}}_2$ monolayer. 2D ${\mathrm{MoS}}_2$ is a quintessential straintronic material for which many experiments have been performed. First, we determine the equilibrium atomic structure which is not known experimentally and is strictly needed to correctly determine the straintronic properties. That enables us to precisely analyze the quasiparticle band gaps for any applied biaxial strain, which we describe by a bivariate paraboloid function of lattice constant and internal structural parameter. Using the fixed-node QMC calculations fitted by analytical formulas, we localize the following excited state crossings between the direct, $\mathrm{K}\to \mathrm{K}$, and indirect $\mathrm{\Gamma }\to \mathrm{X}$ and $\mathrm{K}\to \mathrm{K}$/2 excitations. Based on this highly accurate many-body treatment, we predict a gauge factor of 136 meV/% for the $\mathrm{K}\to \mathrm{K}$ transition and a fairly narrow window of $\approx 2.8$% from compressive to mildly tensile strains, accounting for only $\approx 0.3$ eV band gap change maintaining the direct character of the gap. Consequently, we suggest that, compared to other 2D materials, such as phosphorene, there is only a limited straintronic tuneability in this material often studied for its straintronic properties. QMC results are compared to results of standard DFT modeling, which reveal insights into the corresponding inaccuracies and therefore open a window for educated use of rapid DFT approaches.

We revisited spin dynamics in archetypical classical spin-glass (SG) systems, such as ${\mathrm{Cu}}_{1-x}{\mathrm{Mn}}_x$ $(x=0.017, 0.034, \text{and}0.067)$ dilute alloys and iron aluminosilicate glass, using a modern neutron scattering spectrometer with high neutron flux. The former is crystalline, and the latter is amorphous, where their SG state is well separated from magnetically ordered phases. Bose-scaled localized magnetic excitations were observed in both compounds below the spin-freezing temperature $\left(T_{\mathrm{f}}\right)$. The spectrum exhibits a maximum at low energy and a broad tail on the high-energy side. The excitation energy tends to be higher for the material with higher $T_{\mathrm{f}}$. Above $T_{\mathrm{f}}$, the spectrum considerably changes with temperature, thereby indicating the emergence of the magnetic relaxation process. The magnetic excitation in the SG state has much in common with the boson peak in structural glasses. We consider that the Bose-scaled broad excitation peak is an elementary excitation inherent in disordered systems.

The notion of scale-invariant dynamics is well established at late times in quantum chaotic systems, as illustrated by the emergence of a ramp in the spectral form factor (SFF). Building on the results of the preceding Letter [Phys. Rev. Lett. 131, 060404 (2023)], we explore features of scale-invariant dynamics of survival probability and SFF at criticality, i.e., at eigenstate transitions from quantum chaos to localization. We show that, in contrast to the quantum chaotic regime, the quantum dynamics at criticality do not only exhibit scale invariance at late times, but also at much shorter times that we refer to as mid-time dynamics. Our results apply to both quadratic and interacting models. Specifically, we study Anderson models in dimensions three to five and power-law random banded matrices for the former, and the quantum sun model and the ultrametric model for the latter, as well as the Rosenzweig-Porter model.

Shubnikov-de Haas (SdH) oscillations are the fingerprint of the Landau and Zeeman splitting level structure on the resistivity in presence of a moderate magnetic field before full quantization is manifest in the integer quantum Hall effect. These oscillations have served as a paradigmatic experimental probe and tool for extracting key semiconductor parameters such as carrier density, effective mass $m^{*}$, Zeeman splitting with g factor $g^{*}$, quantum scattering time, and Rashba $\alpha$ and Dresselhaus $\beta$ spin-orbit (SO) coupling parameters. Analytical descriptions of the SdH oscillations are available for some special cases, but no analytical solution could be found for the vast majority of parameter space with all three terms present, usually relevant for experiments. Despite over 50 years of experiments and many theoretical models, which were put forth, this has seriously hampered the analysis and interpretation of experimental data. Here, we bridge this gap by providing an analytical formulation for the SdH oscillations of 2D electron gases (2DEGs) with simultaneous Rashba, Dresselhaus, and Zeeman interactions over a very broad range of parameter space. We use a Poisson summation formula for the density of states of the 2DEG, which affords a complete yet simple description of the oscillatory behavior of its magnetoresistivity. Our analytical and numerical calculations allow us to extract the beating frequencies, quantum lifetimes, and also to understand the role of higher harmonics in the SdH oscillations. More importantly, we derive a simple condition for beating-free SdH oscillations for all harmonics in 2DEGs $\alpha /\beta ={[(1-\tilde{\mathrm{\Delta }})/(1+\tilde{\mathrm{\Delta }})]}^{1/2}$, where $\tilde{\mathrm{\Delta }}\propto g^{*}{m}^{*}$ is a material parameter given by the ratio of the Zeeman and Landau level splitting. This condition is notably different from that of the persistent spin helix at $\alpha /\beta =1$ for materials with large $g^{*}{m}^{*}$ such as InAs or InSb. We also predict beatings in the higher harmonics of the SdH oscillations and elucidate the inequivalence of the SdH response of Rashba-dominated ($\alpha >\beta$) vs Dresselhaus-dominated ($\alpha <\beta$) 2DEGs in semiconductors with substantial $g^{*}$. We find excellent agreement with recent available experimental data of Dettwiler et al. [Phys. Rev. X 7, 031010 (2017)], and Beukman et al. [Phys. Rev. B 96, 241401(R) (2017)]. The formalism builds the foundation for a generation of quantum transport experiments in quantum materials with unprecedented physical insight and material parameter extraction.

Few-layer (FL) transition metal dichalcogenides have been found to exhibit discrete subbands, called van der Waals quantum well (vdWQW) states, resulting from out-of-plane quantum confinement. In this study, we reveal the twisted-resonant tunneling characteristics of a vdWQW device using a three-layer (3L) $\mathrm{W}{\mathrm{Se}}_2/h$-BN/3L-$\mathrm{W}{\mathrm{Se}}_2$ junction with different twist angles ${\theta }_{\mathrm{tunnel}}$ between the two 3L $\mathrm{W}{\mathrm{Se}}_2$ flakes. Using an ambipolar graphene contact to $\mathrm{W}{\mathrm{Se}}_2$, two primary vdWQW states of 3L $\mathrm{W}{\mathrm{Se}}_2$ located in the conduction band (CB) and valence band (VB) were investigated. We found that while the current peak positions due to the electron resonant tunneling between the CB-QW states significantly change with ${\theta }_{\mathrm{tunnel}}$ having a periodicity of ${60}^{\circ }$, the hole resonant tunneling between the VB-QW states exhibits no ${\theta }_{\mathrm{tunnel}}$ dependence; these are due to different angular dispersions of two vdWQWs. The results highlight the different twistronic properties of CB and VB vdWQWs in FL $\mathrm{W}{\mathrm{Se}}_2$.

We investigate the properties of a two-dimensional spinor microcavity polariton system driven by a linearly polarized continuous pump. In particular, we establish the role of the elementary excitations, namely, the so-called half-vortices and full vortices; these objects carry a quantum rotation only in one of the two, or both, spin components, respectively. Our numerical analysis of the steady state shows that it is only the half-vortices that are present in the vortex-antivortex pairing and dissociation responsible for the Berezinskii-Kosterlitz-Thouless transition. These are the relevant elementary excitations close to the critical point. However, by exploring the phase-ordering dynamics following a sudden quench across the transition we prove that full vortices become the relevant excitations away from the critical point in a deep quasi-ordered state at late times. The time scales for half-vortices binding into full vortices are much faster than the vortex-antivortex annihilations.