Indium oxide is widely used as a transparent conducting oxide. Interstitial hydrogen $\left({\mathrm{H}}_i\right)$ acts as a shallow donor, but is expected to be quite mobile, thus enabling potential applications in electrochemical synapses or electrochemical random-access memory. Understanding the diffusion of interstitial hydrogen is essential for controlling its incorporation and stability. Using first-principles calculations based on hybrid density functional theory we find that the proton is the most stable charge state for Fermi levels up to 0.77 eV above the conduction-band minimum. Based on the nudged elastic band method we find that local hopping of the H atom, corresponding to a realignment of the O-H bond, can occur with an activation energy of 0.24 eV; this process can thus occur at low temperatures but does not lead to long-range diffusion. The long-range migration path of ${\mathrm{H}}_i^{+}$ can be decomposed into rotations of the hydrogen atom around oxygen atoms and jumps between two oxygen atoms, with an overall activation energy of 0.94 eV. We compare our results with recent experiments, finding excellent agreement in both the low-temperature and high-temperature regimes, but leading to a re-evaluation of the measured activation energy. Our results provide insight into the different physical mechanisms that govern hydrogen motion in the different temperature regimes, and highlight the necessity of including the quantum-mechanical behavior of protons at low temperature.

Finding hidden order within disorder is a common interest in material science, wave physics, and mathematics. The Riemann hypothesis, stating the locations of nontrivial zeros of the Riemann zeta function, tentatively characterizes statistical order in the seemingly random distribution of prime numbers. This famous conjecture has inspired various connections with different branches of physics, recently with non-Hermitian physics, quantum field theory, trapped-ion qubits, and hyperuniformity. Here we develop the computing platform for the Riemann zeta function by employing classical scattering of light. We show that the Riemann hypothesis suggests the landscape of semi-infinite optical scatterers for the perfect reflectionless condition under the Born approximation. To examine the validity of the scattering-based computation, we investigate the asymptotic behaviors of suppressed reflections with the increasing number of scatterers and the emergence of multiple scattering. The result provides another bridge between classical physics and the Riemann zeros, exhibiting the design of wave devices inspired by number theory.

Antiferromagnetic spin-1 chains host the celebrated symmetry-protected topological Haldane phase, whose spin-$1/2$ edge states were evidenced in bulk by, e.g., electron spin resonance (ESR). To fully reveal and manipulate the spin-$1/2$ degree of freedom, one may build on the recent success in assembling effective spin-1 antiferromagnetic chains from nanographene and porphyrin molecules, and on the nascent technique of combined ESR and scanning tunneling microscopy, which is able to measure the spin dynamics site by site with atomic real-space resolution. In this Letter, we combine exact diagonalization and density matrix renormalization group to investigate the local dynamic spin structure factor of the different phases of the bilinear-biquadratic Hamiltonian with single-ion anisotropy in the presence of an external magnetic field. We find that the signature of the Haldane phase is a low-energy peak created by singlet-triplet transitions in the edge-state manifold. We predict that the signature peak is experimentally observable, although for chains of length above $N=30$ its energy should be first tuned by application of an external magnetic field. We fully characterize the peak in real space and energy, and further show its robustness to weak anisotropy and a relevant range of temperatures.

The altermagnet candidate $\mathrm{M}{\mathrm{n}}_5\mathrm{S}{\mathrm{i}}_3$ has attracted wide attention in the context of nonrelativistic spin physics, due to its composition of light elements. In this study, we demonstrate a hallmark of altermagnetism in $\mathrm{M}{\mathrm{n}}_5\mathrm{S}{\mathrm{i}}_3$ thin films, namely the three options, or variants, for the checkerboard distribution of the magnetic Mn atoms. The magnetic symmetries were altered by field-rotation of the Néel vector along relevant crystal directions, resulting in anomalous Hall effect anisotropy. The experimental results in nanoscale devices were corroborated by a theoretical model involving atomic site dependent anisotropy and bulk Dzyaloshinskii-Moriya interaction for a single variant. These findings elevate $\mathrm{M}{\mathrm{n}}_5\mathrm{S}{\mathrm{i}}_3$ from a candidate to a proven altermagnet.

It is known that ferroelectric single crystals can be turned from a polydomain to a monodomain state by the application of an electric field. Here we report an unexpected opposite effect: the formation of through-the-crystal polydomain pattern in a monodomain ${\mathrm{BaTiO}}_3$ crystal in response to the applied electric field favoring the initial orientation of the polarization. The effect is achieved for special electric field direction which equally selects two domain states, which are present in the polydomain pattern. At the formation of the pattern, the new wedge domains propagate from the sides of the sample in the direction transverse to the electric field. The observations are rationalized in terms of a simple analytical model treating energies of competing domain configurations as functions of the electric field. The results of the analytical treatment are supported by phase field modeling.

Recently, the successful synthesis of the pentagonal form of the ${\mathrm{PdTe}}_2$ monolayer ($p\text{−}{\mathrm{PdTe}}_2$) was reported [Liu et al., Nat. Mater. 23, 1339 (2024)]. In this paper, we present an extensive first-principles density-functional theory based computational study of vacancies in this material. Our paper covers the evolution of the electronic, optical, and magnetic properties of various defect configurations and compares those to the pristine monolayer ($p\text{−}{\mathrm{PdTe}}_2$). We find that $V_{\mathrm{Pd}}$ ($V_{\mathrm{Te}}$) is the most stable defect in the $p\text{−}{\mathrm{PdTe}}_2$ monolayer with 0.95 (1.60) eV of formation energy in the Te-rich (Pd-rich) limit. The defects alter the electronic properties of the monolayer significantly, leading to changes in their magnetic and optical properties due to the emergence of midgap impurity states. The defect complex $V_{\mathrm{Pd}+4\mathrm{Te}}$ is found to induce spin polarization in the system with a total magnetic moment of 1.87 ${\mu }_B$. The obtained low diffusion energy barrier of 1.13 eV (in-plane) and 0.063 eV (top-bottom) corresponding to $V_{\mathrm{Te}}$ indicates its facile migration probability is higher in the top-bottom direction in comparison to the in-plane direction at room temperature, as revealed by ab initio molecular dynamics simulations as well. In order to guide the experimentalists, we also simulated the scanning tunneling microscope images corresponding to all the defect configurations. Moreover, we also computed the electron-beam energies required for creating monovacancies. In the optical absorption spectra of the defective configurations, finite peaks appear below the band edge that are unique to the respective defective configuration. We have also computed the excess polarizability of the defective configurations with respect to the pristine one and found that maximum changes occur in the infrared and visible regions, providing insights into the change in their optical response as compared to the pristine monolayer. Our paper will open prospects of defect engineering in this and related materials with the aim of tuning their electronic, optical, and magnetic properties from the point of view of device applications.

Scale-free localization in non-Hermitian systems is a distinctive type of localization where the localization length of certain eigenstates, known as scale-free localized (SFL) states, scales proportionally with the system size. Unlike skin states, where the localization length is independent of the system size, SFL states maintain a spatial profile that remains invariant as the system size changes. We consider a model involving a single non-Hermitian impurity in an otherwise Hermitian one-dimensional lattice. Introducing disorder into this system transforms SFL states into Anderson-localized states. In contrast to the Hatano-Nelson model, where disorder typically leads to the localization of skin states and a size-independent Anderson transition, the scale-free localization in our model causes a size-dependent Anderson transition.

Interface between metal and disordered semiconductor is commonly required to establish Ohmic contact. However, this requirement is not necessarily beneficial for thermoelectric applications, where heat transfer needs to be taken into account. This study systematically examines interface disorder effects using resistance network and kinetic Monte Carlo method, identifying a parameter space where all thermoelectric properties improve. Within the identified parameter space, the density of localized states varies, while the charge concentration keeps the same as in the bulk. It differs from Ohmic contact requirement, for which interface charge accumulation is beneficial. Thermopower increase is found as a result of filtering out the low-energy electrons by the interface layer. Simulation of the charge carrier dynamics reveals higher transport energies at the interfaces, implying local interface Seebeck coefficient greater than in the bulk. Conductivity increases because of better coupling between the extended electron states in metal and localized states in semiconductor, which is visualized as more uniform electric current at the interface. Relation of the model interface parameters to various effects, materials, and morphologies is discussed, along with relation to recent experiment by Petsagkourakis et al. [Adv. Sci. 10, 2206954 (2023)], where the thermoelectric properties are shown to change not because of interface doping but rather owing to presence of a tunneling barrier.

By tuning the superconducting order parameter with an applied magnetic field, we use neutron diffraction to compare the magnetically ordered phases in superconducting and normal states of ${\mathrm{CeCo}}_{0.5}{\mathrm{Rh}}_{0.5}{\mathrm{In}}_5$. At zero applied field, ${\mathrm{CeCo}}_{0.5}{\mathrm{Rh}}_{0.5}{\mathrm{In}}_5$ displays both superconductivity ($T_c=1.3\mathrm{K}$) and spatially long-ranged commensurate $\uparrow \downarrow \uparrow \downarrow$ antiferromagnetism [$T_N=2.5\mathrm{K}$, propagation vector $\vec{Q}=(\frac{1}{2},\frac{1}{2},\frac{1}{2})$]. Neutron spectroscopy fails to measure propagating magnetic excitations from this ground state with only temporally overdamped fluctuations observable. On applying a magnetic field which suppresses superconductivity, we find anisotropic behavior in the static magnetism. When the applied magnetic field is along the crystallographic $c$ axis, no change in the static magnetic response is observable. However, when the field is oriented within the $a\text{−}b$ plane, an increase in $T_N$ and change in the critical response are measured. At low temperatures in the superconducting phase, the elastic magnetic intensity increases linearly ($\propto \left|H\right|$) with small $a\text{−}b$ oriented fields. However, this trend is interrupted at intermediate fields where commensurate block $\uparrow \uparrow \downarrow \downarrow$ magnetism with propagation vector $\vec{Q}=(\frac{1}{2},\frac{1}{2},\frac{1}{4})$ forms. For large applied fields in the $\left[1\overline{1}0\right]$ direction which completely suppresses superconductivity, weakly incommensurate magnetic order along $L$ is observed to replace the commensurate response present in the superconducting and vortex phases. We discuss experimental considerations related to this shift in momentum and suggest field-induced incommensurate static magnetism, present in the normal state of superconducting and antiferromagnetic ${\mathrm{CeCo}}_{0.5}{\mathrm{Rh}}_{0.5}{\mathrm{In}}_5$ for $a\text{−}b$ plane oriented magnetic fields. We speculate that these field-dependent properties are tied to the field-induced anisotropy associated with the local ${\mathrm{Ce}}^{3+}$ crystal field environment of the tetragonal “115” structure.

Understanding spin wave (SW) damping and how to control it to the point of being able to amplify SW-mediated signals is one of the key requirements to bring envisaged magnonic technologies to fruition. Even widely used magnetic insulators with low magnetization damping in their bulk, such as yttrium iron garnet, exhibit a 100-fold increase in SW damping due to inevitable contact with metallic layers in magnonic circuits, as observed in very recent experiments [Bertelli et al., Adv. Quantum Technol. 4, 2100094 (2021)] mapping SW damping in a spatially resolved fashion. Here, we provide a microscopic and rigorous understanding of wave-vector-dependent SW damping using the extended Landau-Lifshitz-Gilbert equation with a nonlocal damping tensor instead of conventional local scalar Gilbert damping, as derived from Schwinger-Keldysh nonequilibrium quantum field theory. In this picture, the origin of nonlocal magnetization damping and thereby induced wave-vector-dependent SW damping is the interaction of localized magnetic moments of a magnetic insulator with conduction electrons from the three different types of metallic overlayers examined: normal, heavy, and altermagnetic. Due to the spin-split energy-momentum dispersion of conduction electrons in the latter two cases, the nonlocal damping is anisotropic in spin and space, and it can be dramatically reduced by changing the relative orientation of the two layers when compared to the usage of normal metal overlayer.

Nonequilibrium control of electronically ordered hidden phases may lead to the development of ultrafast switches and memory devices. In this study, we demonstrate tunable hidden orders in the half-filled photodoped two-orbital extended Hubbard model. Using steady-state nonequilibrium dynamical mean-field theory, we clarify the coexistence and interplay of nonthermal charge, spin, and orbital order. The hidden state at low effective temperature and sufficiently high photodoping is reminiscent of Kugel-Khomskii order in the two-orbital Hubbard model at $\frac{1}{4}$ and $\frac{3}{4}$ filling, but it emerges out of a nonequilibrium charge-ordered state and exhibits a different magnetic structure. A low-energy effective Hamiltonian is used to analyze the exchange processes that stabilize the nonthermal order.

The pressure dependence of the thermodynamic critical field $B_{\mathrm{c}}$ in elemental indium (In) and tin (Sn) superconductors was studied by means of muon-spin rotation/relaxation. Pressure enhances the deviation of $B_{\mathrm{c}}\left(T\right)$ from the parabolic behavior expected for a typical type-I superconductor, suggesting a weakening of the coupling strength $\alpha =\langle \mathrm{\Delta }\rangle /k_{\mathrm{B}}{T}_{\mathrm{c}}$ ($\langle \mathrm{\Delta }\rangle$ is the average value of the superconducting energy gap, $T_{\mathrm{c}}$ is the transition temperature, and $k_{\mathrm{B}}$ is the Boltzmann constant). As pressure increases from 0.0 to $\simeq 3.0$ GPa, $\alpha$ decreases linearly, approaching the limiting weak-coupling Bardeen-Cooper-Schrieffer (BCS) value ${\alpha }_{\mathrm{BCS}}\simeq 1.764$. Analysis of the data within the framework of Eliashberg theory reveals that only part of the pressure effect on $\alpha$ can be attributed to the hardening of the phonon spectra, reflected by a decrease in the electron-phonon coupling constant. Nearly 40% of the effect is caused by an increased anisotropy of the superconducting energy gap.

Although micro-focused Brillouin light scattering (BLS) has been used for more than 20 years, it lacks a complete theoretical description. This complicates the analysis of experimental data and significantly limits the information that can be obtained. To fill this knowledge gap, we have developed a semi-analytical model based on the mesoscopic continuous medium approach. The model consists of the following steps: calculation of the incident electric field and the dynamic susceptibility, calculation of the induced polarization, and calculation of the emitted electric field and its propagation towards the detector. We demonstrate the model on the examples of the measurements of thermal and coherently excited spin waves. However, the used approach is general and can describe any micro-focused Brillouin light scattering experiment. The model can also bring new analytical approaches to mechanobiology experiments or to characterization of acoustic wave-based devices.

We present results of a comprehensive experimental study of the compound $\mathrm{SmCrTi}{\mathrm{O}}_5$, belonging to the $R{M}_2{\mathrm{O}}_5$ family, where $M$ is a mixture of two transition metals, $\mathrm{C}{\mathrm{r}}^{3+}$ and $\mathrm{T}{\mathrm{i}}^{4+}$. The studies were carried out using temperature-dependent synchrotron x-ray- and neutron-powder diffraction, and measuring the temperature- and field dependences of magnetization. No structural transition is observed between 2 and 450 K. The crystal structure of $\mathrm{SmCrTi}{\mathrm{O}}_5$ is described in the orthorhombic space group Pbam. It is built from $M{\mathrm{O}}_5$ square pyramids and $M{\mathrm{O}}_6$ octahedra. The $\mathrm{S}{\mathrm{m}}^{3+}$ cations occupy a polyhedron of coordination 8, which shares edges with the two other polyhedra. $\mathrm{C}{\mathrm{r}}^{3+}$ and $\mathrm{T}{\mathrm{i}}^{4+}$ are found to differentially occupy each of the two transition-metal coordination sites, forming two substructures. Magnetic $d^3\mathrm{C}{\mathrm{r}}^{3+}$ ions occupy the octahedra which share edges to form chains, while nonmagnetic $d^0 \mathrm{T}{\mathrm{i}}^{4+}$ ions occupy the pyramids. Magnetic susceptibility curves present a broad signal below 195 K with a maximum at about 100 K, characteristic of 1D antiferromagnetism. Nevertheless, long-range 3D magnetic order appears below 12 K as evidenced by neutron-powder diffraction. The refined magnetic structure is in addition supported by electronic structure calculations. From these data, a model of spin ordering in the ground state is proposed. Since the structural features are characteristic of alternating Heisenberg antiferromagnetic chains, the magnetic properties of $\mathrm{SmCrTi}{\mathrm{O}}_5$ are compared with its $\mathrm{SmCrGe}{\mathrm{O}}_5$ analog for which a spin gap was evidenced.

We study the impact of hole doping on the Kitaev-Heisenberg model on the honeycomb lattice. We investigate the pairing tendencies and correlation functions in the framework of a $t-J-K$ model using density matrix renormalization group calculations on three-leg cylinders. In the case of the pure Kitaev model, which realizes a quantum spin-liquid phase at half-filling, we find that binding of two holes only occurs at low values of the hopping, where the holes are slow. We have theoretically verified that pair formation occurs in the limit of immobile holes, where the pure Kitaev model remains exactly solvable. When we instead fix the hopping at an intermediate, more realistic, value, and vary the Heisenberg and Kitaev interaction strengths, we find pairing tendencies only in the Néel phase. This is in contrast to prior mean-field calculations, highlighting the importance of accounting for the kinetic energy of dopants in generalized Kitaev models. Interestingly, we also find signatures of pair-density wave formation over the studied range of model parameters, namely, a periodic modulation of the charge density as well as the spin-spin and pair-pair correlations in real space. Moreover, we present a comparative study of the different correlations as a function of doping. We finally discuss the potential for experimentally observing the studied physics in quantum materials and heterostructures.

Chirality induced spin selectivity is a spin-polarized phenomenon resulting from a helical structure with a considerably effective spin-orbit coupling. The large spin polarization observed in chiral organic molecules is remarkable due to their weak spin-orbit coupling. To understand the origin of the counterintuitive experimental results, we study the transport properties of single-stranded DNA under strong electronic correlation utilizing renormalized mean-field theory and Landauer-Büttiker formulas. By introducing a strong correlation, the spin polarization is significantly enhanced and reaches 46.5% near the metal-insulator transition, which is consistent with previous experiments. Furthermore, we study the impact of the coupling at the contact interface and the size dependence of the system.

We present a comparison of various approximations to the self-consistent $GW$ methods, including the one-shot $G_0{W}_0$ method, different quasiparticle self-consistent schemes, and the fully self-consistent $GW$ $\left(\mathrm{sc}GW\right)$ approach. To ensure an unbiased and equitable comparison, we have implemented all the schemes with the same underlying Matsubara formalism, while employing Gaussian orbitals to describe the system. Aiming to assess and compare different $GW$ schemes, we analyze band gaps in semiconductors and insulators, as well as ionization potentials in molecules. Our findings reveal that for solids, the different self-consistent schemes perform very similarly. However, for molecules, full self-consistency outperforms all other approximations, i.e., the one-shot and quasiparticle self-consistent $GW$ methods. Our work highlights the importance of implementation details when comparing different $GW$ methods. By employing state-of-the-art fully self-consistent, finite temperature $GW$ calculations, we have successfully addressed discrepancies in the existing literature regarding its performance. Our results also indicate that when stringent thresholds are imposed, the $\mathrm{sc}GW$ method consistently yields accurate results.