In this paper, we report on the experimental demonstration of single-slit diffraction exhibited by electrons propagating in encapsulated graphene with an effective de Broglie wavelength corresponding to their attributes as massless Dirac fermions. Nanometer-scale device designs were implemented to fabricate a single-slit followed by five detector paths. Predictive calculations were also utilized to readily understand the observations reported. These calculations required the modeling of wave propagation in ideal case scenarios of the reported device designs to more accurately describe the observed single-slit phenomenon. This experiment was performed at room temperature and 190 K, where data from the latter highlighted the exaggerated asymmetry between electrons and holes, recently ascribed to slightly different Fermi velocities near the $K$ point. This observation and device concept may be used for building diffraction switches with versatile applicability.

Excitons hosted by GaN/(Al,Ga)N quantum wells (QWs) are spatially indirect due to the giant built-in electric field that separates electrons and holes along the growth direction. This electric field, and thus exciton energy, can be reduced by depositing metallic layers on the sample surface. Using spatially resolved microphotoluminescence spectroscopy we compare the effects of two different materials, nickel/gold (NiAu) and few-layer graphene (FLG), on the potential landscape experienced by the excitons. We are able to (i) determine the potential barriers imposed on QW excitons by deposition of FLG and NiAu to be 14 and 82 meV, respectively, and (ii) to evince their impact on the exciton transport at appropriate densities. Optical losses and inhomogeneous broadening induced by deposition of NiAu and FLG layers are similar, and their joined implementation constitute a promising tool for electrostatic modulation of exciton densities even in the absence of any applied electric bias.

Higher-order topological insulators (HOTIs), that are classified as obstructed atomic insulators (OAIs) in the topological quantum chemistry (TQC) theory, attract great interest owning to the lower-dimensional topological boundary states. However, the boundary states in HOTIs reported so far are often fragile, manifested as strongly depending on crystalline symmetries and cleavage terminations in the disk or cylinder geometry. Here, using the TQC theory, we propose an intuitive strategy to establish the connection between the obstructed Wannier charge centers of OAIs and the emergence of robust corner states in two-dimensional systems. Based on first-principles calculations and real space invariant theory, we extend the concept of OAIs to phonon systems and thereby predict that the robust corner states can be realized in the phonon spectra of $M{X}_3$ ($M$ = Bi, Sb, As, Sc, Y; $X$ = I, Br, Cl) monolayers. The phonon corner modes in different shapes of nanodisks are investigated, and their robustness facilitates the detection in experiments and further applications. This work suggests a promising avenue to explore more attractive features of higher-order band topology beyond the existing paradigm.

Time-dependent driving holds the promise of realizing dynamical phenomena absent in static systems. Here, we introduce a correlated random driving protocol to realize a spatiotemporal order that cannot be achieved even by periodic driving, thereby extending the discussion of time translation symmetry breaking to randomly driven systems. We find a combination of temporally disordered micromotion with prethermal stroboscopic spatiotemporal long-range order. This spatiotemporal order remains robust against generic perturbations, with an algebraically long prethermal lifetime where the scaling exponent strongly depends on the symmetry of the perturbation, which we account for analytically.

Chiral $d$-wave superconductivity has been proposed in a number of different materials, but characteristic experimental fingerprints have been largely lacking. We show that quadruply quantized coreless vortices are prone to form and offer distinctive signatures of the chiral $d$-wave state in both the local density of states and the total magnetic moment. Their dissimilarity in positive versus negative magnetic fields leads to additional spontaneous symmetry breaking, producing clear evidence of time-reversal symmetry breaking, chiral superconductivity, and the Chern number.

Quantized conductance plateaus, a celebrated hallmark of Majorana bound states (MBSs) predicted a decade ago, have recently been observed with small deviations in iron-based superconductors and hybrid nanowires. Here, we demonstrate that nearly quantized conductance plateaus can also arise from trivial Andreev bound states (ABSs). To avoid ABS interruptions, we propose identifying ABS-induced quantized conductance plateaus by measuring the associated differential current noise $P$ versus bias voltage $V$. Specifically, for a quantized conductance plateau induced by one or multiple low-energy ABSs, the associated $P\left(V\right)$ curve exhibits a double-peak around zero bias, with the peak positions at $e\left|V\right|\approx 3k_{B}T$ (where $T$ is the temperature) and peak values larger than $2e^3/h$. These features greatly contrast those of an MBS or quasi-MBS, whose $P\left(V\right)$ curve displays a broad zero-bias dip and is consistently below $2e^3/h$. This protocol can be practically implemented in a variety of MBS candidate platforms using an electrode or STM tip as a probe.

The projector augmented wave method has been used to compute the iron $L_{2,3}$ edges of x-ray absorption spectra (XAS) and x-ray magnetic circular dichroism (XMCD) of the spin-crossover $\mathrm{Fe}{\left(\mathrm{phen}\right)}_2{\left(\mathrm{NCS}\right)}_2$ molecule when adsorbed on Cu(001) surface and in the gas phase, for both the high-spin (HS) and low-spin (LS) states. The electronic structures of both HS and LS states have been calculated using the spin-polarized generalized gradient approximation for the exchange-correlation potential, and the strongly localized iron $3d$ states are described using Dudarev's rotationally invariant formulation of the $\text{DFT}+\text{U}$ method. It is shown that only the iron all-electron partial waves are necessary to calculate the XAS transition matrix elements in the electric dipole approximation, as the contribution of the pseudo partial waves is compensated by the plane-wave component of the wave function. It is found that the calculated XAS and XMCD with the static core hole or the Slater transition state half hole are in less good agreement with experiment than those using the so called initial state. This disagreement is due to the reduction of the iron spin magnetic moment caused by the static screening of the core hole by the photo-electron. The $L_{2,3}$ XAS formula is found to be directly related to the unoccupied $3d$ density of states (DOS), and hence the symmetry broken $e_g$ and the $t_{2g}$ iron DOS are used to explain the XAS and XMCD results. It is demonstrated that the dependence of the HS XMCD on the direction of incident x-ray circularly polarized light with respect to the magnetization direction can be used to determine the iron octahedron deformation, while the XMCD for various magnetization directions is directly related to the anisotropy of the orbital magnetic moment and the magnetocrystalline energy. The Thole-Carra-Van der Laan XMCD sum rules have been applied to the XMCD $L_{2,3}$ spectra to compute the spin and orbital magnetic moments. It is shown that the magnetic dipole moment $T_z$ is very large due to the strong distortion of the iron octahedron and is necessary for an accurate determination of the sum rule computed spin magnetic moment.

Engineering Gilbert damping in ferromagnetic metal films is of great importance to exploit and design spintronic and high-frequency electromagnetic devices. The spin-orbit parameter $\xi$ has been found to be efficient for tuning the Gilbert damping rate ${\alpha }_{\mathrm{G}}$ in a wide range. However, the theoretically predicted cubic (quadratic) scaling of the conductivity-like ${\alpha }_{\sigma }$ (resistivity-like ${\alpha }_{\rho }$) part of ${\alpha }_{\mathrm{G}}$ on $\xi$ has not been verified in real ferromagnetic metal materials. To clarify this relationship, herein, we focus on the damping mechanism in oriented hcp ${\mathrm{Co}}_{1-x}{\mathrm{Ir}}_x$ soft magnetic films by combining ferromagnetic resonance measurements with first-principle calculations. The ${\alpha }_{\mathrm{G}}$ is found to increase linearly as the Ir concentration $x$ changes from 0.02 to 0.23, where $\xi$ is dominant over other related parameters. In particular, we demonstrate the ${\xi }^{2.51} \left({\xi }^{1.69}\right)$ dependence of ${\alpha }_{\sigma }$ (${\alpha }_{\rho }$) in oriented hcp ${\mathrm{Co}}_{1-x}{\mathrm{Ir}}_x$ soft magnetic films by extracting ${\alpha }_{\sigma }$ and ${\alpha }_{\rho }$ according to the temperature dependence of ${\alpha }_{\mathrm{G}}$, which validates the theoretical prediction. The difference in the $\xi$ dependence of the two types of damping is mainly derived from the non-negligible variation in the density of states at the Fermi surface ($D_{\mathrm{E}f}$) induced by $\xi$. The present results provide a deeper insight into the Gilbert damping mechanism and suggest an approach to tailor the magnetic damping freely in magnetic metallic materials.

The $\mathrm{Ni}{\left(\mathrm{NCS}\right)}_2{\left(\mathrm{pyzdo}\right)}_2$ coordination polymer is found to be an $S=1$ spatially anisotropic square lattice with easy-axis single-ion anisotropy. This conclusion is based upon considering in concert the experimental probes x-ray diffraction, magnetic susceptibility, magnetic-field-dependent heat capacity, muon-spin relaxation, neutron diffraction, neutron spectroscopy, and pulsed-field magnetization. Long-range antiferromagnetic (AFM) order develops at $T_N=18.5\mathrm{K}$. Although the samples are polycrystalline, there is an observable spin-flop transition and saturation of the magnetization at $\approx 80\mathrm{T}$. Linear spin-wave theory yields spatially anisotropic exchanges within an AFM square lattice, $J_x=0.235\mathrm{meV}$, $J_y=2.014\mathrm{meV}$, and an easy-axis single-ion anisotropy $D=-1.622\mathrm{meV}$ (after renormalization). The anisotropy of the exchanges is supported by density functional theory.

We elaborate that $s$-wave and $d$-wave superconductors described by mean field theories possess a nontrivial quantum geometry. From the overlap of two quasihole states at slightly different momenta, one can define a quantum metric that measures the distance in the curved momentum space. The momentum integration of the quantum metric represents an average distance that we call the fidelity number, which may be further expressed as a fidelity marker defined locally on every lattice site. For $s$-wave superconductors, we unveil that the quantum metric generally influences the electromagnetic responses at finite wavelength, such as the infrared absorption and paramagnetic current. In addition, the dielectric response is directly proportional to the fidelity number, which is found to be determined by the coherence length and suppressed by disorder. For $d$-wave superconductors, we demonstrate the singular behavior of the quantum metric near the nodal points, and a metric-curvature correspondence between the azimuthal quantum metric and the non-Abelian Berry connection that integrates to a topological charge of the nodal points.

We study a superconducting heterojunction with one side characterized by the unconventional chiral $p$-wave gap function $p_x\pm i{p}_y$ and the other side the conventional $s$-wave one. Though a relative phase of $\pm \frac{\pi }{2}$ between any two components of gap functions is favored in the junction region, mutual phase differences cannot achieve $\pm \frac{\pi }{2}$ simultaneously, which results in frustration. Based on a Ginzburg-Landau free-energy analysis, the frustrated pattern is determined to be $s+i{\eta }_1[exp(i{\eta }_2\phi /2)p_x+{\eta }_{3}exp(-i{\eta }_2\phi /2)p_y]$ with ${\eta }_j=\pm 1$ ($j=1,2,3$), where $\phi$ is the phase difference between the $p_x$- and $p_y$-wave gap functions. Furthermore, we find that the junction exhibits an anisotropic magnetoelectric effect, manifesting itself as an anisotropic spin magnetization along the edge of the junction.

Ab initio investigations of the structural, electronic, and dynamical properties of the high-temperature $\beta$ phase of copper pyrophosphate were performed using density functional theory. The electronic band structure shows the Mott insulating state due to electron correlations in the copper ions. By calculating phonon dispersion relations, the soft mode at the $A$ point of the Brillouin zone was revealed, showing the dynamical instability of the $\beta$ phase at low temperatures. The double-well potential connected with the soft mode is derived and the mechanism of the structural phase transition to the $\alpha$ phase is discussed. The self-consistent phonon calculations based on the temperature-dependent effective potential show the stabilization of the $\beta$ phase at high temperatures, due to the anharmonic effects. The pronounced temperature dependence and the large linewidth of the soft mode indicate an essential role of anharmonicity in the structural phase transition.

Dissipation is inevitable in realistic quantum circuits. We examine the effects of dissipation on a class of monitored random circuits that exhibit a measurement-induced entanglement phase transition. This transition has previously been understood as an order-to-disorder transition of an effective classical spin model. We extend this mapping to include on-site dissipation described by the dephasing and amplitude damping channel and study the corresponding 2D Ising model with generalized interactions and develop diagrammatic methods for the exact Boltzmann weights of the bonds in terms of probability of measurement $p$, the dissipation rate $\mathrm{\Gamma }$, and the on-site Hilbert space dimension $q$. The dissipation plays the role of ${\mathbb{Z}}_2$-symmetry-breaking interactions, while small measurement rates reduces the ratio of the symmetry-breaking interactions to the pairwise interactions, conducive to long-range order. We analyze the dynamical regimes of the Rényi mutual information and find that the joint action of monitored measurements and dissipation yields short time, intermediate time and steady-state behavior that can be understood in terms of crossovers between different classical domain wall configurations. The presented analysis applies to monitored open or Lindbladian quantum systems and provides a tool to understand entanglement dynamics in realistic dissipative settings and achievable system sizes.

Newly published diffraction data on hexagonal $\mathrm{YMn}{\mathrm{O}}_3$ at a temperature of 10 K are shown to be consistent with a trusted expression of the magnetic symmetry, although the data alone are not definitive [M. Ramakrishnan et al., Phys. Rev. Res. 5, 013203 (2023)]. Howard et al. conclude from an exhaustive review of experimental data that the symmetry of the antiferromagnetic motif of Mn ions is most likely $P{6}_3{}^{\prime }c{m}^{\prime }$ [C. J. Howard et al., Acta Crystallogr. B 69, 534 (2013).]. The data reported by Ramakrishnan et al. do not eliminate symmetry $P{6_3}^{\prime }$ from our calculated diffraction patterns, because the studied reflection vector is parallel to the common chiral vector associated with each triangle of Mn axial dipole moments. Proposed diffraction patterns will give decisive statements about the magnetic symmetry in future investigations using resonant x-ray and magnetic neutron diffraction. To this end, both axial magnetism and polar magnetism in the multiferroic material are essential in the analysis of diffraction patterns. We study polar magnetism in symmetry $P{6}_3{}^{\prime }c{m}^{\prime }$ using Dirac multipoles, including Mn anapoles. They also feature in amplitudes for magnetic neutron diffraction together with Dirac quadrupoles, previously shown to account for diffraction by pseudogap phases of cuprate superconductors.

We construct a solvable Lindblad model in arbitrary dimensions, in which the Liouvillian can be mapped to a BCS-Hubbard model featuring an imaginary Hubbard interaction. The Hilbert space of the system can be divided into multiple sectors, each characterized by an on-site invariant configuration. The model exhibits bistable steady states in all spatial dimensions, which is guaranteed by the fermion-number parity. Notably, the Liouvillian gap exhibits a Zeno transition, below which the Liouvillian gap is linear with respect to the dissipation. We also uncover a generic dimension-dependent gap behavior: In one dimension, the gap originates from multiple sectors with spectral crossing; in higher dimensions, a single sector determines the gap.

The concept of Wannier-Stark ladders, describing the equally spaced spectrum of a tightly bound particle in a constant electric field, is generalized to account for arbitrary slowly varying potentials. It is shown that an abrupt transition exists that separates Wannier-Stark-like from effective-mass-like behavior when the depth of the perturbation becomes equal to the width of the band of extended states. For potentials bounded from below, the spectrum bifurcates above the critical energy while the wavefunctions detach from the effective-mass region and split into two pieces.

This Letter describes a simple mechanism for superconducting pairing with finite wave vector (pair density wave) based on weak coupling. The mechanism is illustrated with a quasi-one-dimensional model relevant to certain a class of quasi-one-dimensional materials. Within this model, pair and charge density wave order parameters are intertwined emerging as components of the same matrix field and are related by particle-hole symmetry.

The search for optimal Rashba semiconductors with large Rashba constants, strong electric field responses, and potential thermoelectric properties is pivotal for spin field-effect transistors (SFETs) and Rashba thermoelectric devices. Herein, we employ first-principles calculations to explore the intrinsic Rashba spin splitting in a series of two-dimensional (2D) $XY{Z}_2$ (X, $Y=\mathrm{Si}$, Ge, Sn; $X\ne Y$; $Z=\mathrm{P}$, As, Sb, Bi) monolayers via unnatural inverse Janus structural design. Instead of common Janus-type Rashba systems, the $\mathrm{SiSn}{\mathrm{Sb}}_2$ and $\mathrm{GeSn}{\mathrm{Sb}}_2$ monolayers within inverse Janus structures are first predicted as ideal Rashba systems with isolated spin-splitting bands near the Fermi level, and the Rashba constants ${\alpha }_{\mathrm{R}}$ are calculated as 0.94 and $1.27\mathrm{eV}\AA$, respectively. More importantly, the Rashba effect in such $\mathrm{SiSn}{\mathrm{Sb}}_2$ and $\mathrm{GeSn}{\mathrm{Sb}}_2$ monolayers can be more efficiently modulated by the external electric field compared to the biaxial or uniaxial strain, especially with $\mathrm{GeSn}{\mathrm{Sb}}_2$ monolayer exhibiting a strong electric field response rate of $1.34\mathrm{e}{\AA }^2$, leading to a short channel length, $L=64\mathrm{nm}$. Additionally, owing to the inapplicability of work function and potential energy in assessing built-in electric field $\left(E_{in}\right)$ in inverse Janus $\mathrm{SiSn}{\mathrm{Sb}}_2$ and $\mathrm{GeSn}{\mathrm{Sb}}_2$ structures, we further propose an effective method to characterize $E_{in}$ through a view of fundamental charge transfer to approximately quantize the ${\alpha }_{\mathrm{R}}$ and its variation under an external electric field. Our work not only proposes the $\mathrm{GeSn}{\mathrm{Sb}}_2$ monolayer acting as a promising multifunctional material for potential applications in SFETs and Rashba thermoelectric devices but also inspires future research to introduce Rashba spin splitting in 2D materials through inverse Janus design.

We study a bilayer of the frustrated $J_1\text{−}{J}_2$ Heisenberg model on the square lattice. Starting from the dimer limit at strong interlayer coupling, we perform series expansions using the perturbative continuous unitary transformation, based on the flow equation method, in order to determine the spectrum up to the two-triplon sector. From the one-triplon dispersion, we obtain quantum critical lines for transitions from the dimer phase into either Néel or collinear magnetic order. For low to intermediate frustration these transitions are consistent with existing findings, based on the magnetic phases. In the region of strongest frustration, i.e., $J_2/J_1\sim 0.5$, we provide an estimate for the stability of the anticipated single-layer quantum spin-liquids against finite interlayer coupling. In the two-triplon sector, we find a set of well defined (anti)bound states, which can be classified according to total spin and in-plane rotational symmetry. For vanishing frustration, these states agree with the previous series expansion analysis. For $J_2/J_1\gtrsim 0.5$, we provide evidence for a close-by condensation of one-triplon and two-triplon singlet bound states, suggesting that between the dimer and the collinear state additional phases may intervene.

We present experimental and theoretical studies of the magneto-optical properties of $n$-type ${\mathrm{InAs}}_x{\mathrm{P}}_{1-x}$ films in ultrahigh magnetic fields at room temperature. We compare Landau level and band structure calculations with observed cyclotron resonance (CR) measurements and extract effective $g$-factors and CR masses for two different alloy concentrations, $x=0.07$ and $x=0.34$. In addition, we employ time-resolved magneto-optical Kerr measurements on these ternary alloys to explore the spin relaxation time. These alloys have immense prospects for quantum communication devices and $g$-factor engineering, and our study provides insights into this underexplored narrow-gap system.