We present a systematic investigation of the in-plane anomalous Hall effect (IPAHE) induced by the in-plane magnetization in single-crystalline Fe(211) films epitaxially grown on MgO(110) substrates. A single-crystal domain in the Fe(211) films is well controlled using slightly miscut substrates, enabling precise observation of the IPAHE. A pronounced IPAHE is observed when the magnetization aligns along the $\mathrm{Fe}\left[\overline{1}11\right]$ direction, with the in-plane anomalous Hall resistivity ${\rho }_{\mathrm{IPAH}}$ reaching its maximum value and showing independence from the current direction. This behavior aligns with phenomenological models dictated by crystalline symmetry and likely stems from epitaxial strain in the films. The scaling relationship between ${\rho }_{\mathrm{IPAH}}$ and the longitudinal resistivity across a range of temperatures and film thicknesses is systematically analyzed. A nonmonotonic temperature dependence of ${\rho }_{\mathrm{IPAH}}$ indicates a complex interplay between extrinsic and intrinsic mechanisms. Our study provides experimental insight into the mechanisms underlying IPAHE and highlights the potential for tailoring IPAHE through film thickness and strain engineering.

The anomalous proximity effect of a spin-triplet $p$-wave superconductor has been known as a part of Majorana physics, and is explained by the penetration of zero-energy states from a surface of a superconductor to a dirty normal metal. We demonstrate that a spin-singlet $d$-wave superconductor without any surface zero-energy states exhibits the anomalous proximity effect in the presence of a specific spin-orbit interaction. The results show the quantization of the zero-bias conductance in a dirty normal-metal/superconductor junction. We also discuss a relation between our findings and results in an experiment on a ${\mathrm{CoSi}}_2\text{/}{\mathrm{TiSi}}_2$ junction.

Employing the gauge representation of crystalline symmetries necessitates capturing their algebraic structure in a projective form. As such, the projectively represented space group (PRSG) offers a powerful framework for uncovering novel topological phases and enhancing our understanding of topological band theory. Meanwhile, the tunable ${\mathbb{Z}}_2$ gauge field inherent in artificial crystals underpins the practical implementation of PRSG. Indeed, the PRSG mechanism has fueled significant progress in discovering new topological phases within photonic and phononic crystals (PnCs). In this work, we incorporate projectively translational symmetry into elastic wave PnCs and demonstrate the resulting emergence of Möbius edge states. Beyond exhibiting a ${\mathbb{Z}}_2$ topological phase that diverges from the conventional two-dimensional Su-Schrieffer-Heeger model, our system also offers controllability over Möbius edge states: by simply adjusting the coupling tubes, the fourfold degeneracy at high-symmetry points can be shifted, accompanied by the concurrent displacement of the Möbius edge states. These findings not only demonstrate the introduction of negative coupling in elastic wave PnCs but also leverage projectively translational symmetry—realized through such negative coupling—to both realize and precisely manipulate Möbius edge states. Our results thus establish a fundamental platform for devising topological phases based on PRSG in elastic wave systems.

We study in detail the postselection problem in a specific model: bosons hopping on a lattice subjected to continuous local measurements of quadrature observables. We solve the model analytically and show that the postselection overhead can be reduced by postprocessing the entire measurement record into one or two numbers for each trajectory and then binning trajectories based only on these numbers. Based on this simplification, we formulate a step-by-step protocol designed to recover connected two-point functions of the quantum trajectories, which display an exponentially decaying profile that is not observable in the unconditional, trajectory averaged, state. We also test this protocol numerically in a way that utilizes only experimentally accessible information, showing that various quantum trajectory observables can be recovered with a few repetitions of the numerical experiment, even after including inevitable coarse-graining procedures expected under realistic experimental conditions. We finalize by providing experimental implementations of these models in cavity-QED and circuit-QED platforms.

The interaction of terahertz (THz) radiation with high-frequency spin resonances in complex magnetic materials is central for modern ultrafast magnonics. Here we demonstrate strong variations of the excitation efficiency of the sub-THz exchange magnon in a single crystal gadolinium iron garnet (${\mathrm{Gd},\mathrm{Bi})}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$. An enhancement of the exchange magnon amplitude is observed when its frequency matches an eigenmode of the cavity created by the sample interfaces. Moreover, this enhancement is accompanied by a fivefold decrease in effective damping of the exchange mode. The THz-exchange magnon interaction in the cavity is analyzed within the developed Landau–Lifshitz–Gilbert formalism for three coupled magnetization sublattices and cavity-enhanced THz field. This work presents an approach for the THz excitation of magnetization dynamics in ferrimagnets and outlines promising pathways for the controlled optimization of light-magnetization coupling in single crystals.

We revisit the renormalization group (RG) analysis of the Kohn-Luttinger (KL) mechanism for superconductivity. The KL mechanism leads to superconductivity in a system with a repulsive bare interaction. The key ingredient is the screening effect that renders the induced interaction attractive in channels with nonzero angular momentum $\ell \ne 0$, thereby triggering the Bardeen-Cooper-Schrieffer (BCS) instability. According to the original argument, the resulting gap is exponentially small, with its exponent scaling as $-{\ell }^4$. However, the KL mechanism was originally formulated within perturbation theory, where the series is known to converge poorly in certain cases—most notably, for the $p$-wave paring gap induced by a repulsive $s$-wave contact interaction. This poor convergence may be attributed to a divergent integrand in a specific class of diagrams containing both the BCS logarithm and the Kohn anomaly, suggesting that one must resum the Kohn anomaly contributions separately from the BCS logarithm. In this work, we incorporate the Kohn anomaly contribution into the $\beta$ function of the RG equation governing the BCS instability near the Fermi surface. Our solution shows that the KL gap exponent is then proportional to $-\ell$, indicating a significant enhancement of the KL mechanism beyond the previously known result. To illustrate this, we study the spin-triplet $p$-wave pairing gap arising from a repulsive $s$-wave contact interaction and compare our RG-based results with those obtained from the Bethe-Salpeter equation in perturbation theory.

Charge-neutral graphene in the quantum Hall regime is an example of a quantum Hall ferromagnet in a complex spin-valley space. This system exhibits a plethora of phases, with the particular spin-valley order parameters chosen by the system depending sensitively on the short-range anisotropic couplings, the Zeeman field, and the sublattice symmetry breaking field. A subset of order parameters related to lattice symmetry breaking have been observed by scanning tunneling microscopy. However, other order parameters, particularly those that superpose spin and valley, are more elusive, making it difficult to pin down the nature of the phase. We propose a solution to this problem by examining two types of experimentally measurable quantities: transport gaps and collective mode dispersions. We find that the variation of the transport gap with the Zeeman and sublattice symmetry-breaking fields, in conjunction with the number of Larmor and gapless modes, provides a unique signature for each theoretically possible phase.

Altermagnetism, as an unconventional antiferromagnetism, exhibits collinear-compensated magnetic order in real space and spin-splitting band structure in reciprocal space. In this work, we propose a general approach to generating multicomponent structures with two-dimensional (2D) altermagnetism, based on symmetry analysis. Specifically, by analyzing the space group of the crystal structures and their subgroups, we systematically categorize equivalent atomic positions and arrange them into orbits based on symmetry operations. Chemical elements are then allowed to occupy all atomic positions on these orbits, generating candidate structures with specific symmetries. We present a general technique for generating collinear-compensated magnetic order, characterized by the symmetrical interconnection between opposite-spin sublattices, and employ first-principles calculations to determine magnetic ground states of multicomponent materials. This approach integrates symmetry analysis with the screening of altermagnetic configurations to evaluate the likelihood of candidates possessing altermagnetism. To verify the methodology, we provide examples of previously unreported 2D altermagnets, such as ${\mathrm{Cr}}_2{\mathrm{Si}}_2{\mathrm{S}}_3{\mathrm{Se}}_3, {\mathrm{Fe}}_2{\mathrm{P}}_2{\mathrm{S}}_3{\mathrm{Se}}_3$, and ${\mathrm{V}}_2{\mathrm{O}}_2\mathrm{Br}{\mathrm{I}}_3$, and evaluate their dynamical stability by calculating the phonon spectrum. The results demonstrate the feasibility of our approach in generating stable multicomponent structures with two-dimensional altermagnetism. Our research has significantly enriched the candidate materials for 2D altermagnets, and provides a reference for experimental synthesis.

Mixed anion halide-chalcogenide materials have attracted considerable attention due to their exceptional optoelectronic properties, making them promising candidates for various applications. Among these, ${\mathrm{CuBiSeCl}}_2$ has recently been experimentally identified with remarkably low lattice thermal conductivity (${\kappa }_L$). In this study, we employ Wigner transport theory combined with neuroevolution machine learning potential-assisted self-consistent phonon calculations to unravel the microscopic origins of this low ${\kappa }_L$. Our findings reveal that the delocalization and weak bonding of copper atoms are key contributors to the strong phonon anharmonicity and wavelike tunneling (random walk diffusons). These insights deepen our understanding of the relationship between bonding characteristics, anharmonicity, delocalization, and vibrational dynamics, paving the way for the design and optimization of ${\mathrm{CuBiSeCl}}_2$ and analogous materials for advanced phonon engineering applications.

The optical properties of Janus-type hybrid silicon-gold nanocylinders are theoretically studied. We show that the inhomogeneity of the internal material in these particles causes a strong bianisotropic response. Their lack of inversion symmetry formally determines the bianisotropic response of hybrid nanocylinders. We demonstrate a method for obtaining in advance information on nonzero components of the dipole polarizability tensor of hybrid particles by analyzing the relationship between their symmetry properties and the multipole composition of their eigenmodes. The spectral response of metasurfaces composed of a periodic arrangement of such particles can feature strong resonances associated with multipole coupling and the excitation of quasibound states in the continuum (quasi-BICs). Using the resonant bianisotropic properties of the hybrid particles and the ability to tune the quasi-BICs (trapped modes) to a predetermined wavelength by choosing the metasurface period, we demonstrate the excitation of electric and magnetic types of quasi-BICs in the infrared region. The ability to switch between these types of quasi-BICs by changing the incident light polarization is discussed. We also demonstrate that, unlike purely dielectric metasurfaces, the excitation of the quasi-BICs in hybrid metasurfaces leads to a resonant absorption of light.

Nonreciprocal hopping induces a synthetic magnetic flux which leads to the non-Hermitian Aharonov-Bohm effect. Since non-Hermitian Hamiltonians possess both real and imaginary eigenvalues, this effect allows the observation of real and imaginary persistent currents in a ring threaded by the synthetic flux. Motivated by this, we investigate the behavior of persistent currents in a disordered Hatano-Nelson ring with anti-Hermitian intradimer hopping. The disorder is diagonal and we explore three distinct models, namely, the Aubry-André-Harper model, the Fibonacci model, both representing correlated disorder, and an uncorrelated (random) model. We conduct a detailed analysis of the energy spectrum and examine the real and imaginary parts of the persistent current under various conditions such as different ring sizes and filling factors. Interestingly, we find that real and imaginary persistent currents exhibit amplification in the presence of correlated disorder. This amplification is also observed in certain individual random configurations but vanishes after configuration averaging. Additionally, we observe both diamagnetic and paramagnetic responses in the current behavior and investigate aspects of persistent currents in the absence of disorder that have not been previously explored. Interestingly, we find that the intradimer bonds host only imaginary currents, while the interdimer bonds carry only real currents. The bulk-boundary correspondence is investigated by analyzing the existence of localized edge states under the open boundary condition.

We apply various unsupervised machine learning methods for phase classification to investigate the finite-temperature phase diagram of the spinless Falicov-Kimball model in two dimensions. Using only particle occupation snapshots from Monte Carlo simulations as input, each technique, including a straightforward classification based on principal component analysis (PCA), successfully identifies the phase boundary between ordered and disordered phases, independent of the type of phase transition. Remarkably, these techniques also distinguish between the weakly localized and Anderson-localized regimes within the disordered phase, accurately identifying their crossover, which is a challenging task for standard methods. Among the machine learning approaches used, PCA based analysis outperforms more complex methods, such as neural network predictors and autoencoders. These results underscore the effectiveness of simple unsupervised techniques in examining phase transitions and electron localization in complex correlated systems.

We introduce an attention-based fermionic neural network (FNN) to variationally solve the problem of two-dimensional Coulomb electron gas in magnetic fields, a canonical platform for fractional quantum Hall (FQH) liquids, Wigner crystals, and other unconventional electron states. Working directly with the full Hilbert space of $N$ electrons confined to a disk, our FNN consistently attains energies lower than LL-projected exact diagonalization (ED) and learns the ground state wave function to high accuracy. In low LL mixing regime, our FNN reveals microscopic features in the short-distance behavior of FQH wave function beyond the Laughlin ansatz. For moderate and strong LL mixing parameters, the FNN outperforms ED significantly. Moreover, a phase transition from FQH liquid to a crystal state is found at strong LL mixing. Our study demonstrates unprecedented power and universality of FNN based variational method for solving strong-coupling many-body problems with topological order and electron fractionalization.

It has recently been realized that magnetic systems with coplanar magnetic order that are invariant under the combined operation of time-reversal and translation with half a unit cell feature energy bands with a symmetry-protected $p$-wave spin polarization. Such $p$-wave magnets are a sought-after spin analogy of unconventional triplet superconducting pairing, and they show promise for use in spintronics. Metallic helimagnets provide a realization of $p$-wave magnetism, but such order often occurs in systems lacking inversion symmetry so that Rashba spin-orbit interactions can be prominent. An important question is therefore how the magnitude and the existence of $p$-wave spin polarization is affected by Rashba spin-orbit interaction. Here, we prove that while the $p$-wave symmetry of the spin-polarized bands is strictly speaking removed by such spin-orbit interactions in helimagnets unless the period of the helix is fine-tuned, the actual quantitative deviation from $p$-wave symmetry is extremely weak unless the period of the helix is only a few lattice sites. Thereafter, we show that the $p$-wave magnetism becomes completely robust in pairs of antiferromagnetically coupled helices. More precisely, the $p$-wave spin polarization of the bands then appears regardless of the periodicity and regardless of the strength of the spin-orbit interactions. This shows that antiferromagnetically coupled helimagnetic chains produce robust $p$-wave spin polarization free of fine-tuning requirements, making them attractive for potential spintronic applications.

The antiferromagnetic heavy-fermion compound ${\mathrm{Ce}}_2{\mathrm{RhIn}}_8$ belongs to the same family and bears similarities with the well-studied prototypical material ${\mathrm{CeRhIn}}_5$, which demonstrates a unique behavior under applied magnetic field. Here, we report specific-heat measurements on a high-quality single crystal of ${\mathrm{Ce}}_2{\mathrm{RhIn}}_8$ in magnetic fields up to 35 T applied along both principal crystallographic directions. When the magnetic field is applied along the $a$ axis of the tetragonal crystal structure, two additional field-induced antiferromagnetic phases are observed, in agreement with previous reports. One of them is confined in a small area of the field-temperature phase diagram. The other one, which develops above $\sim 2.5$ T, is very robust against the field. Its transition temperature increases with field, reaches a maximum at $\sim 12$ T, and then starts to decrease. However, it tends to saturate towards the highest field of our measurements. For a field applied along the $c$ axis, the Néel temperature $T_N$ initially decreases with field, as expected for a typical antiferromagnet. Surprisingly, an additional phase emerges above $\sim 10$ T. It is most likely to be of the same origin as its counterpart observed above 2.5 T for the other field orientation. This phase is also unusually robust: Its transition temperature increases all the way up to 35 T, where it exceeds the zero field $T_N=2.85$ K. Finally, for both field directions, the phase diagrams contain rarely observed tricritical points of second-order phase transitions.

We study the edges of fractional quantum spin Hall insulators (FQSH) with half-integer spin Hall conductance. These states can be viewed as symmetric combinations of a spin-up and spin-down half-integer fractional quantum Hall state (FQH) that conserve the z-component of spin. We consider the states based on the non-Abelian Pfaffian, anti-Pfaffian, PH-Pfaffian, and 221 FQHs, and generic Abelian FQHs. For strong enough spin-conserving interactions, we find that all the non-Abelian and Abelian edges flow to the same fixed point that consists of a single pair of charged counter-propagating bosonic modes. If spin-conservation is broken, but time-reversal symmetry is preserved, the Abelian edge can be fully gapped in a time-reversal symmetric fashion. The non-Abelian edge with broken spin-conservation remains gapless due to time-reversal symmetry, and can flow to a new fixed point with a helical gapless pair of Majorana fermions. From this, we conclude that these non-Abelian FQH bilayers realize half-integer fractional topological insulators, protected by time-reversal symmetry. We discuss the possible relevance of our results to the recent observation of a half-integer edge conductance in twisted ${\mathrm{MoTe}}_2$.

Antiskyrmions, as topological quasiparticles, hold significant promise for spintronics and nanoscale data storage applications. Using molecular dynamics simulations based on effective Hamiltonians, we investigated the thermal stability of antiskyrmion nanodomains in rhombohedral barium titanate. At 1 K, antiskyrmions with a topological charge of −2 were found to be the most stable nanodomain state across all diameters examined by us. In our systematic study, the most robust antiskyrmion was found to have a diameter of 4 nm, maintaining its original size, shape, and topological charge up to the characteristic temperature $T$* ≈ 85 K. Domains with diameters between 2.8 and approximately 4.5 nm exhibited fragmentation into six topological defects, termed quarks, each carrying a fractional skyrmion charge of −1/3. For domains larger than 4.5 nm, each topological quark split into two prequarks, each with a charge of −1/6. These larger nanodomains demonstrated increased mobility and a growing tendency for shape and skyrmion charge fluctuations. Above the $T$* temperature, all larger nanodomains gradually shrank to a diameter of about 4 nm before collapsing into a single-domain state. These findings reveal the relatively high stability of antiskyrmions over a broad temperature range, even in the absence of a stabilizing bias field, and emphasize the pivotal role of topological quark dynamics. This establishes barium titanate as a key platform for exploring and applying topological phenomena.

The many-body mobility edge (MBME) in energy, which separates thermal states from many-body localization (MBL) states, is a critical yet controversial concept in MBL physics. Here we examine the quasiperiodic $t_1\text{−}{t}_2$ model that features a mobility edge. With the addition of nearest-neighbor interactions, we suggest the potential existence of a MBME. Then we investigate the impact of a type of bond dissipation on the many-body system by calculating the steady-state density matrix and analyzing the transport behavior and demonstrate that dissipation can cause the system to predominantly occupy either the thermal region or the MBL region, irrespective of the initial state. Finally, we discuss the effects of increasing system size. Our results indicate that dissipation can induce transitions between thermal and MBL states, providing an alternative approach for experimentally determining the existence of the MBME.

We study the one-dimensional spin-1/2 Kitaev-Gamma model with a bond-dependent Dzyaloshinskii-Moriya (DM) interaction, which can be induced by an electric field applied in the third direction where the first and second directions refer to the two bond directions in the model. By a combination of field theory and symmetry analysis, extended gapless phases with an emergent $\mathrm{SU}{\left(2\right)}_1$ conformal symmetry are found in the phase diagram of the spin-1/2 Kitaev-Gamma-DM chain. The analytic predictions are in good agreements with numerical results obtained from density matrix renormalization group simulations.

Magnetic-ferroic ordering and magnetic-toroidal moments are essential concepts in molecular electronics and magnetics. The magnetic toroidal moment is critical in understanding new electronic states and their possible uses. This paper discusses the notion of toroidicity waves. In particular, we present a one-dimensional model of interconnected toroidicity leading to an organization principle around an emergent quantum particle, a carrier of toroidicity waves, dubbed the toroidon. We illustrate some functionalities that could be achieved once control over the toroidon is acquired. We show that a 1D dimerized and ferromagnetic-like spin chain can display ferrotoroidicicity and propose its description in terms of an effective quasi-1D spin chain, marking a crucial step towards further research on the phenomena and potential applications of ferrotoroids.