The evolution of the magnetic structure of Fe-doped MnNiGe alloys of nominal compositions ${\mathrm{MnNi}}_{0.75}{\mathrm{Fe}}_{0.25}\mathrm{Ge}$ and ${\mathrm{Mn}}_{0.85}{\mathrm{Fe}}_{0.15}\mathrm{NiGe}$ has been probed through neutron powder diffraction (NPD) experiments in the presence of external magnetic fields ($H$). Application of external $H$ results in a significant decrease in the antiferromagnetic satellite peak's intensities along with a considerable change in the incommensurate propagation vector ${\mathit{k}}_{\mathrm{AFM}}=(k_a,0,0)$. In addition, a reasonable increase in some of the nuclear reflections has also been noticed, which can clearly be described by the ferromagnetic propagation vector ${\mathit{k}}_{\mathrm{FM}}=(0,0,0)$. Our analysis confirms the gradual rotation of magnetic moments towards the $a$ axis with increasing $H$ and eventual realization of ferromagnetic arrangement at higher applied $H$.

Proximity phenomena and induced superconducting correlations in heterostructures are shown to be strongly affected by the nonlocal nature of the electronic attraction. The latter can trigger the formation of Cooper pairs consisting of electrons localized in neighboring layers even in the absence of direct quasiparticle transfer between the layers. We investigate the manifestations of such nonlocal pairing and resulting unconventional induced superconductivity in an exemplary two-dimensional (2D) electronic system coupled to a conventional superconductor. The interplay between the quasiparticle tunneling and spin-triplet interlayer pairing is shown to generate the odd-frequency superconducting correlations in the 2D material which give rise to the paramagnetic contribution to the Meissner response and affect the energy resolved quasiparticle density of states. Experimental evidence for the above nonlocal interface pairing would provide new perspectives in engineering the unconventional superconducting correlations in heterostructures.

It presents a significant challenge to elucidate the relationship between the phases of open quantum many-body systems and the spectral structure of their governing Liouvillian, which determines how the density matrix evolves. Previous studies have focused on the Liouvillian gap, defined as the decay rate of the most slowly decaying mode, as a key indicator of dissipative phase transition, noting its closure in symmetry-broken phases and opening in disordered phases. In this work, we propose an additional spectral gap, termed the oscillating-mode gap, defined as the decay rate of the most slowly decaying oscillating mode. Through the analysis of a prototype dissipative boson system, we demonstrate the necessity of both the Liouvillian gap and the oscillating-mode gap for the comprehensive characterization of the system's phases and the transitions between them.

The study of thermalization and its breakdown in isolated systems has led to a deeper understanding of nonequilibrium quantum states and their dependence on initial conditions. The role of initial conditions is prominently highlighted by the existence of quantum many-body scars, special athermal states with an underlying effective superspin structure, embedded in an otherwise chaotic many-body spectrum. Spin Heisenberg and $XXZ$ models and their variants in one and higher dimension have been shown to host exact quantum many-body scars, exhibiting perfect revivals of spin helix states that are realizable in synthetic and condensed matter systems. Motivated by these advances, we propose experimentally accessible, local, time-dependent protocols to explore the spatial thermalization profile and highlight how different parts of the system thermalize and affect the fate of the superspin. We identify distinct parametric regimes for the ferromagnetic ($X$-polarized) initial state based on the interplay between the driven spin and the rest, including local athermal behavior where the driven spin effectively decouples, acting like a “cold” spot while being instrumental in heating up the other spins. We also identify parameter regimes where the superspin remains resilient to local driving for long timescales. We develop a real- and Floquet-space picture that explains our numerical observations, and make predictions that can be tested in various experimental setups.

We study classical spin models on the 1/1 Tsai-type approximant lattice using Monte Carlo and mean-field methods. Our aim is to understand whether the phase diagram differences between Gd- and Tb-based approximants can be attributed to anisotropy induced by the crystal-electric field. To address this question, we treat Gd ions as Heisenberg spins and Tb ions as Ising spins. Additionally, we consider the presence of the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction to replicate the experimentally observed correlation between magnetic properties and electron concentration. Surprisingly, our findings show that the transition between ferromagnetic and antiferromagnetic order remains unaltered by the anisotropy, even when accounting for the dipole interaction. We conclude that a more comprehensive model, extending beyond the free-electron gas RKKY interaction, is likely required to fully understand the distinctions between Gd- and Tb-based approximants. Our work represents a systematic exploration of the impact of anisotropy on the ground-state properties of classical spin models in quasicrystal approximants.

We propose a hybrid quantum system consisting of a magnetic particle inductively coupled to two superconducting transmon qubits, where qubit-qubit interactions are mediated via magnons. We show that the system can be tuned into three different regimes of effective qubit-qubit interactions, namely, a transverse ($XX+YY$), a longitudinal ($ZZ$), and a nontrivial $ZX$ interaction. In addition, we show that an enhanced coupling can be achieved by employing an ellipsoidal magnet, carrying anisotropic magnetic fluctuations. We propose a scheme for realizing two-qubit gates, and simulate their performance under realistic experimental conditions. We find that iswap and cz gates can be performed in this setup with an average fidelity $\gtrsim 99\%$, while an icnot gate can be applied with an average fidelity $\gtrsim 88\%$. Our proposed hybrid circuit architecture offers an alternative platform for realizing two-qubit gates between superconducting qubits and could be employed for constructing qubit networks using magnons as mediators.

The effect of the spin-orbit coupling on the ground state properties of the square-lattice three-band Hubbard model with a single electron per site is studied by a generalized Hartree-Fock approximation. We calculate the full phase diagram and show that there appear additional orbital-entangled phases brought about by competition of various exchange channels or by the spin-orbit coupling in addition to conventional states stabilized by the Kugel-Khomskii mechanism. One of these phases previously proposed to explain magnetic properties of ${\mathrm{Sr}}_2{\mathrm{VO}}_4$ is characterized by vanishing dipolar magnetic moments and antiferro-octupolar ordering. We calculated microscopic parameters for this material and demonstrate that it is located near a phase boundary of two orbital-entangled and two conventional antiferromagnetic ferro-orbital states.

The rare-earth Zintl compound $\mathrm{EuI}{\mathrm{n}}_2\mathrm{A}{\mathrm{s}}_2$ has been theoretically recognized as a candidate for realizing an intrinsic antiferromagnetic (AFM) bulk axion insulator and a higher-order topological state, which provides a fertile platform to explore novel topological transport phenomena. However, the axion state has yet to be realized because $\mathrm{EuI}{\mathrm{n}}_2\mathrm{A}{\mathrm{s}}_2$ is highly hole doped. Here, we synthesized a series of high-quality Ca-doped $\mathrm{EuI}{\mathrm{n}}_2\mathrm{A}{\mathrm{s}}_2$ ($\mathrm{C}{\mathrm{a}}_x\mathrm{E}{\mathrm{u}}_{1-x}\mathrm{I}{\mathrm{n}}_2\mathrm{A}{\mathrm{s}}_2$, $x=0\text{–}0.25$) single crystals to tune the Fermi energy above the hole pocket. Our Hall measurements reveal that the Ca substitution decreases the hole carrier density. This decrease is brought by the lattice contraction and the effective electron doping by a slight increase of the valence charge of $\mathrm{C}{\mathrm{a}}_x\mathrm{E}{\mathrm{u}}_{1-x}$ as $x$ increases, confirmed by our first-principles calculations. We further find that both the temperature dependence of the magnetic susceptibility with a local maximum at the Néel temperature and the topological Hall effect originating from the finite real-space spin chirality persist in the Ca-doped samples as observed in pristine $\mathrm{EuI}{\mathrm{n}}_2\mathrm{A}{\mathrm{s}}_2$, despite that the nonmagnetic Ca substitution decreases the effective moment and the Néel temperature. These results show that the Ca substitution tunes the Fermi energy while keeping the AFM magnetic ground state, suggesting that the axion insulating state may be realized by further Ca substitution.

Low-dimensional materials are susceptible to electronic instabilities such as charge density waves (CDWs), originating from a divergence in the Lindhard electron response function, combined with a finite electron-phonon coupling strength. In this paper, we present a detailed characterization of the CDW in the quasi-one-dimensional material CuTe, including (1) direct visualization of lattice distortion seen with noncontact atomic force microscopy in real space, (2) the out-of-plane momentum dependency of the CDW gap size of the quasi-one-dimensional bands by angle-resolved photoemission spectroscopy, and (3) coherent dynamics of a photoexcited phonon mode seen by time- and angle-resolved photoemission spectroscopy, with frequency and wave vector ${\mathit{q}}_{\text{CDW}}$ corresponding to the soft phonon modes predicted by theory. Furthermore, we find that the CDW gap closes through a transient band renormalization. We thus confirm that, despite the quasi-one-dimensional characteristics of CuTe, it hosts inherently three-dimensional CDWs.

The Wilson-Fisher criticality provides a paradigm for a large class of phase transitions in nature (e.g., helium, ferromagnets). In three dimensions, Wilson-Fisher critical points are not exactly solvable due to the strongly correlated feature, so one has to resort to nonperturbative tools such as numerical simulations. Here, we design a microscopic model of Heisenberg magnet bilayer and study the underlying Wilson-Fisher $\mathrm{O}\left(3\right)$ transition through the lens of fuzzy sphere regularization. We uncover a wealth of crucial information which directly reveals the emergent conformal symmetry regarding this fixed point. Specifically, we accurately calculate and analyze the energy spectra at the transition, and explicitly identify the existence of a conserved Noether current, a stress tensor, and relevant primary fields. Most importantly, the primaries and their descendants form a fingerprint conformal tower structure, pointing to an almost perfect state-operator correspondence. Furthermore, by examining the leading rank-4 symmetric tensor operator, we demonstrate the cubic perturbation is relevant, implying the critical $\mathrm{O}\left(3\right)$ model is unstable to cubic anisotropy, in agreement with the renormalization group and bootstrap calculations. The successful dissection of conformal content of the Wilson-Fisher universality class extends the horizon of the fuzzy sphere method and paves the way for exploring higher-dimensional conformal field theories.

Flat bands exhibit many exotic physical phenomena due to the dispersionless features and are receiving widespread attentions. In this work, a metastable bismuthene allotrope (P-3m1-$\mathrm{B}{\mathrm{i}}_{72}$) with isolated flat bands near the Fermi level was identified, through high-throughput tight-binding calculations, from more than 500 allotropes. P-3m1-$\mathrm{B}{\mathrm{i}}_{72}$ features the kagome characteristic of an interlaced distribution of triangles and hexagons. First-principles calculations revealed that this structure is a dynamically stable phase of bismuthene and energetically more favorable than many previously predicted bismuthene allotropes. Based on the high-level functional of HSE06 (HSE stands for Heyd-Scuseria-Ernzerhof), three isolated flat bands are confirmed in the band structures of P-3m1-$\mathrm{B}{\mathrm{i}}_{72}$, located in the vicinity of the Fermi level. These isolated flat bands originate from the kagome-like features of the atomic configuration as well as the charge distributions, and their isolation and flatness are severely affected by the strength of spin-orbital coupling (SOC). Additionally, the spin textures of flat bands in P-3m1-$\mathrm{B}{\mathrm{i}}_{72}$ are k dependent and exhibit twofold rotation symmetry in reciprocal space. Our work provides a candidate material for studying the properties of isolated flat bands in a strong SOC system.

Nonequilibrium transport in hybrid semiconductor-superconductor nanowires is crucial for many quantum phenomena such as generating entangled states via cross Andreev reflection (CAR) processes, detecting topological superconductivity, reading out Andreev spin qubits, coupling spin qubits over long distances, and so on. Here, we investigate numerically transport properties of a proximitized Rashba nanowire that hosts spin-polarized low-energy quasiparticle states. We show that the spin polarization in such one-dimensional Andreev bands, extended over the entire nanowire length, can be detected in nonlocal transport measurements with tunnel-coupled side leads that are spin polarized. Remarkably, we find an exact correspondence between the sign of the nonlocal conductance and the spin density of the superconducting quasiparticles at the side lead position. We demonstrate that this feature is robust to moderate static disorder. As an example, we show that such a method can be used to detect spin inversion of the bands, accompanying the topological phase transition (TPT) for realistic system parameters. Furthermore, we show that such effects can be used to switch between CAR and elastic cotunneling (ECT) processes by tuning the strength of either the electric or the magnetic field. These findings hold significant practical implications for state-of-the-art transport experiments in such hybrid systems.

Monolayer molybdenum disulfide ($\mathrm{Mo}{\mathrm{S}}_2$) is a prominent two-dimensional semiconductor material known for its high theoretical intrinsic mobility. However, when implemented in transistors, the mobility significantly decreases. To investigate the mechanisms behind this reduction, several theoretical models have been developed to correlate device mobility with temperature. Despite these efforts, the accuracy of existing models remains limited due to the simplified calculation for lattice phonon scattering limited mobility (${\mu }_{\mathrm{ph}}$) and lack of appropriate temperature consideration for the localized charge trap (LCT) effect. In this paper, we present a theoretical model to address the mobility degradation in monolayer $\mathrm{Mo}{\mathrm{S}}_2$ transistors by thoroughly reevaluating ${\mu }_{\mathrm{ph}}$ and the LCT effect. The temperature and electron concentration dependence of ${\mu }_{\mathrm{ph}}$ was calculated with full ab initio scattering rates in the Boltzmann transport equation framework. Additionally, the temperature-dependent parameters (energy range and density of LCT) were proposed to evaluate the LCT effect rationally. Our model accurately fits various electron transport mechanisms for monolayer $\mathrm{Mo}{\mathrm{S}}_2$ transistors, particularly those dominated by lattice phonon scattering or dominated by LCT effects. The validation and broad applicability of the model offer a robust approach for quantitatively analyzing the electron transport mechanisms of monolayer $\mathrm{Mo}{\mathrm{S}}_2$ transistors.

The experimental realization of the quantum Kibble-Zurek mechanism in arrays of trapped Rydberg atoms has brought the problem of commensurate-incommensurate transition back into the focus of active research. Relying on equilibrium simulations of finite intervals, direct chiral transitions at the boundary of the period-3 and period-4 phases have been predicted. Here, we study how these chiral transitions can be diagnosed experimentally with critical dynamics. We demonstrate that chiral transitions can be distinguished from the floating phases by comparing Kibble-Zurek dynamics on arrays with different numbers of atoms. Furthermore, by sweeping in the opposite direction and keeping track of the order parameter, we identify the location of conformal points. Finally, combining forward and backward sweeps, we extract all critical exponents characterizing the transition.

Non-Hermitian systems exhibit novel phenomena without Hermitian counterparts, such as exceptional points and the non-Hermitian skin effect. These non-Hermitian topological phenomena are observable in single-particle excitations of correlated systems in equilibrium, which are described by Green's functions. In this paper we demonstrate the appearance of the hinge non-Hermitian skin effect in the effective Hamiltonian that describes the single-particle properties of an $f$-electron system. Skin effects result in a strong sensitivity to boundary conditions, and a large number of eigenstates localize at one boundary when open boundary conditions are applied. Our system exhibits such sensitivity and hosts skin modes localized around hinges. This hinge skin effect is induced by a non-Hermitian topology of the surface Brillouin zone. The hinge skin modes are observed for one-dimensional subsystems located between one pair of exceptional points in the surface Brillouin zone. This paper highlights that correlated materials are an exciting platform for analyzing non-Hermitian phenomena.

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