Incompressibility plays a key role in the geometric description of fractional quantum Hall fluids. It is naturally related to quantum area-preserving diffeomorphisms and the underlying Girvin-MacDonald-Plazman algebra, which gives rise to an emergent nonrelativistic massive spin-2 mode propagating in the bulk. The corresponding metric tensor can be identified with a nematic order parameter for the bulk states. In the linearized regime with a flat background, it has been shown that this mode can be described by a spin-2 Schrödinger action. However, quantum area-preserving diffeomorphisms also suggest the existence of higher-spin modes that cannot be described through nematic fractional quantum Hall states. Here, we consider p-atic Hall phases, in which the corresponding p-atic order parameters are related to higher-rank symmetric tensors. We then show that in this framework, nonrelativistic massive chiral higher-spin fields naturally emerge and that their dynamics is described by higher-spin Schrödinger actions. We finally show that these effective actions can be derived from relativistic massive higher-spin theories in $2+1$ dimensions after taking a nonrelativistic limit.

We study nonequilibrium steady-state transport in a boundary driven one-dimensional fermionic lattice setup which is further subjected to particle loss. We analyze the system size scaling of conductance at zero temperature for different values of the chemical potential of the boundary reservoirs. We consider a variety of loss channel configurations: (i) single loss at the middle site of the lattice, (ii) multiple but nonextensive lossy channels, and (iii) extensive lossy channels. For the cases (i) and (ii), the conductance scaling with system size remains robust (i.e., same as the case with no loss) for chemical potential within and outside the lattice band, while at the band edge rich anomalous conductance scaling emerges. For case (iii), the conductance scaling becomes ballistic in the thermodynamic limit for any value of chemical potential. We explain the emergence of these different system size scalings of conductance by analyzing the spectral properties of the associated non-Hermitian transfer matrices of the underlying lattice. We demonstrate that the emergence of anomalous scaling is deeply connected to the existence of exceptional points of transfer matrices. Our study unravels that by carefully optimizing the loss mechanism configurations, one can in principle realize systems with rich transport properties in low-dimensional open quantum systems.

The energy spectrum of topological semimetals contains protected degeneracies in reciprocal space that correspond to Weyl, Dirac, or multifold fermionic states. To exploit the unconventional properties of these states, one has to access the electronic structure of the three-dimensional bulk. In this paper, we present a joint theory-experiment study of the electronic structure of a candidate topological semimetal with resonant inelastic x-ray scattering (RIXS). We resolve the bulk electronic states of FeSi using momentum-dependent RIXS at the Fe $L_3$ edge. We observe a broad excitation continuum devoid of sharp features, consistent with particle-hole scattering in an underlying electronic band structure. Using density functional theory (DFT), we calculate the electronic structure of FeSi and derive a band theory formulation of RIXS in the fast collision approximation to model the scattering process with zero adjustable parameters. While band theory predicts an excitation continuum with broad spectral features similar to the observed ones, discrepancies between theory and experiment suggest the presence of low-energy processes that DFT alone does not account for. This study of RIXS in a topological semimetal shows that RIXS is a useful tool for revealing unanticipated behavior of bulk electronic states in this class of materials.

We present strain tuning of excitonic emission in monolayer ${\mathrm{MoSe}}_2$ by using a high-temperature physical vapor deposition (PVD). The use of two amorphous substrates, ${\mathrm{Si}}_3{\mathrm{N}}_4$ and ${\mathrm{SiO}}_2$, provides two setpoints to induce distinct amounts of biaxial tensile strain determined by a thermal expansion mismatch between the monolayer and the substrate. The tuning rate of the $A$-exciton transition energy is found to be 103 meV/% by photoluminescence (PL), which represents the highest value realized by biaxial strain in transition metal dichalcogenides. The biaxial nature of the tensile strain is confirmed by polarization-resolved second harmonic generation, which reveals unperturbed in-plane threefold symmetry of the monolayer. Furthermore, a softening of $A_{1\mathrm{g}}$ out-of-plane lattice vibration is identified in the Raman spectroscopy, which is known to be insignificant for uniaxial strain. Concomitantly, PL mapping of our PVD monolayers demonstrates that (i) larger strain occurs in the interior of the monodomain islands compared to the edges and (ii) the absence of island-size dependence in the magnitude of induced strain. Our results demonstrate an effective path toward strain engineering of excitons by using growth substrates, which holds great promise as a building block for future optoelectronic applications.

Using the transfer matrix method, we numerically investigate the structure of spatial coherences and their fluctuations in the three-dimensional (3D) Anderson model in the metallic phase when driven out of equilibrium by external leads at zero temperature and in linear response. We find that the stationary state entails nonlocal non-Gaussian correlations in the longitudinal direction, which are characteristic of diffusive nonequilibrium steady states. These correlations are quantitatively matched, at least up to third order, by those analytically derived in the quantum symmetric simple exclusion process (QSSEP) which describes diffusive fermions in 1D subject to dynamical disorder. Furthermore, the large deviation scaling and $U\left(1\right)$ invariance of these correlations imply a link between the Anderson model and free probability theory. Our findings suggest the existence of a universal structure of correlations in noninteracting diffusive quantum systems that might be captured by QSSEP.

Initializing the ground state of a quantum bit (qubit) based on Majorana zero modes is one of the most pressing issues for future topological quantum computers. We explore a protocol for initializing such topological qubits based on magnet-superconductor hybrid networks by coupling magnetic chains to a single molecule magnet. The parity of the Majorana state is converted to the presence or absence of a Yu–Shiba–Rusinov state at the molecule. The coupling can be activated by switching the spin state of the molecule, allowing the ground-state parity of the chain to be controlled. We demonstrate that initialization with either parity for a Majorana qubit can be achieved. We then introduce the augmented Majorana qubit, which includes the state of the molecule in the definition of the logical qubit. Using this definition we can initialize a qubit without high-precision timing.

The Holstein model on a square lattice at half-filling has a well-established finite temperature phase transition to an insulating state with long range charge density wave (CDW) order. Because this CDW formation suppresses pairing, a superconducting (SC) phase emerges only with doping. In this work, we study the effects of dilution of the local phonon degrees of freedom in the Holstein model while keeping the system at half filling. We find not only that the CDW remains present up to a dilution fraction $f\sim 0.15$, but also that long range pairing is stabilized with increasing $f$, resulting in a supersolid regime centered at $f\approx 0.10$, where long range diagonal and off-diagonal correlations coexist. Further dilution results in a purely SC phase, and ultimately in a normal metal. Our results provide a new route to the supersolid phase via the introduction of impurities at fixed positions which both increase quantum fluctuations and also are immune to the competing tendency to phase separation often observed in the doped case.

Understanding open quantum systems using information encoded in its complex eigenvalues has been a subject of growing interest. In this Letter, we study higher-order gap ratios of the singular values of generic open quantum systems. We show that the $k\mathrm{th}\text{−}\mathrm{order}$ gap ratio of the singular values of an open quantum system can be connected to the nearest-neighbor spacing ratio of positions of classical particles of a harmonically confined log gas with inverse temperature ${\beta }^{\prime }\left(k\right)$, where ${\beta }^{\prime }\left(k\right)$ is an analytical function that depends on $k$ and the Dyson's index $\beta =1$, 2, and 4 that characterizes the properties of the associated Hermitized matrix. Our findings are crucial not only for understanding long-range correlations between the eigenvalues but also provide an excellent way of distinguishing different symmetry classes in an open quantum system. To highlight the universality of our findings, we demonstrate the higher-order gap ratios using different platforms such as non-Hermitian random matrices, random dissipative Liouvillians, Hamiltonians coupled to a Markovian bath, and Hamiltonians with built-in non-Hermiticity.

Using an efficient first-principles computational approach, we investigate the influence of the thermal longitudinal spin fluctuations (LSFs) within the nickel sublattices on the thermoelastic properties of ${\mathrm{Ni}}_3\mathrm{Nb}$ with ${\mathrm{D}0}_{22}$ structure. Leveraging the mean magnetic moment values to represent the spin-fluctuation state at respective temperatures and incorporating the lattice vibration contributions via the Debye model, the equilibrium bulk parameters and elastic constants are derived. We find that, although the volume expansion remains the primary mechanism behind the softening of the elastic constants with increasing temperature, the LSFs effect contributes significantly to the temperature dependence of $c_{11}$ and $c_{33}$. Our analysis reveals that including the LSFs makes the theoretical thermal-expansion coefficient highly anisotropic, in line with the experiments. Quantitative agreement between theory and experiment is obtained for the thermal expansion along the $c$ axis at temperatures up to 500 K, whereas the measured thermal expansion along the $a$ axis is underestimated by theory. The present results provide theoretical thermoelastic data for free-standing ${\mathrm{Ni}}_3\mathrm{Nb}$ precipitates with ${\mathrm{D}0}_{22}$ structure, which can be used to estimate the lattice strains around such precipitates in Ni-based superalloys.

The bulk-boundary correspondence in topological crystalline insulators (TCIs) links the topological properties of the bulk to robust observables on the edges, e.g., the existence of robust edge modes or fractional charge. In one dimension, TCIs protected by reflection symmetry have been realized in a variety of systems in which each unit cell has spatially distributed degrees of freedom (SDOF). However, these realizations exhibit sensitivity of the resulting edge modes to variations in edge termination and to the local breaking of the protective spatial symmetries by inhomogeneity. Here we demonstrate topologically protected edge states in a monoatomic, orbital-based TCI that mitigates both of these issues. By collapsing all SDOF within the unit cell to a singular point in space, we eliminate the ambiguity in unit-cell definition and hence remove a prominent source of boundary termination variability. The topological observables are also more tolerant to disorder in the orbital energies. To validate this concept, we experimentally realize a lattice of mechanical resonators where each resonator acts as an “atom” that harbors two key orbital degrees of freedom having opposite reflection parity. Our measurements of this system provide direct visualization of the $sp$-hybridization between orbital modes that leads to a nontrivial band inversion in the bulk.

We posit the existence of a nonthermal phase transition in iron, driven by a loss of ferromagnetic ordering on ultrafast timescales with increasing electron temperature. The transition corresponds to a solid-solid bcc to fcc phase transformation and takes place at an electron temperature of 0.62 eV while the ion lattice remains near room temperature. The bcc structure initially undergoes phonon softening during the magnetic transformation, followed by a solid-solid phase transition to the fcc structure, and a subsequent hardening of phonon modes. We present a detailed physical picture of the process, supported by finite-temperature density functional theory simulations of the phonon dispersion curves, electronic density of states, and thermodynamic free energy.

We systematically investigate the effects of Kitaev interaction on magnetic orders and anisotropy in both triangular and honeycomb lattices on the classical level. Our study highlights the critical role of the Kitaev interaction in modulating phase boundaries and predicting new phases, e.g., zigzag phase in triangular lattice and AABB phase in honeycomb lattice, which are absent with pure Heisenberg interactions. Moreover, we reveal the special state-dependent anisotropy of Kitaev interaction, and develop a general method that can determine the presence of Kitaev interaction in different magnets. It is found that the Kitaev interaction does not induce anisotropy in some magnetic orders such as ferromagnetic order, while it can cause different anisotropy in other magnetic orders. Furthermore, we emphasize that the off-diagonal $\mathrm{\Gamma }$ interaction also contributes to anisotropy, competing with the Kitaev interaction to reorient spin arrangements. Our work establishes a framework for comprehensive understanding the impact of Kitaev interaction on ordered magnetism.

Absence of net magnetization in altermagnets is both a blessing (no stray fields) and a curse (no obvious way to manipulate altermagnetic domains by external fields). Yet, MnTe was demonstrated experimentally to have no measurable stray fields and yet controllable by external magnetic field—a win-win situation. In this paper, we discuss possible mechanisms driving this ultrasmall canting of Mn moments and, most importantly, the microscopic mechanism of coupling the canting with the altermagnetic order. It appears to be a higher (third) order effect in (already small) spin-orbit coupling, which explains the unusually weak, barely measurable ferromagnetism in MnTe. Microscopic understanding of the beneficial properties of MnTe opens a road to controllable design of similar altermagnets for spintronics applications.

Nanopatterned magnetic thin films offer a platform for exploration of tailored magnetic properties such as emergent long-range order. A prominent example is artificial spin ice (ASI), where an arrangement of nanoscale magnetic elements, acting as macrospins, interact via their dipolar fields. In this study, we discuss the transition from antiferromagnetic (AFM) to ferromagnetic (FM) long-range order in a square lattice ASI as the magnetic elements are gradually rotated through $45{}^{\circ }$ to a “pinwheel” configuration. The AFM-FM transition is observed experimentally using synchrotron radiation x-ray spectromicroscopy and occurs for a certain rotation angle of the nanomagnets, dependent on the dipolar coupling strength determined by the separation of the magnets in the lattice. Large-scale magnetic dipole simulations show that the point-dipole approximation fails to capture the correct AFM-FM transition angle. However, excellent agreement with experimental data is obtained using a dumbbell-dipole model, which better reflects the actual dipolar fields of the magnets. This model also explains the coupling dependence of the transition angle, another feature not captured by the point-dipole model. Our findings resolve a discrepancy between measurement and theory in previous work on “pinwheel” ASIs and establish the coupling dependence of the AFM-FM transition. The revised dipole model, with a more accurate representation of the stray field, offers more precise control of magnetic order in artificial spin systems.