The magnetic structure, magnetoresistance (MR), and Hall effect of the noncentrosymmetric magnetic semimetal NdAlGe are investigated, revealing an unusual magnetic state and anomalous transport properties that are associated with the electronic structure of this compound. The magnetization and MR measurements are both highly anisotropic and indicate an Ising-like magnetic system. The magnetic structure is complex in that it involves two magnetic ordering vectors, including an incommensurate spin density wave and commensurate ferrimagnetic state in zero field. We have discovered a large anomalous Hall conductivity that reaches $\approx 430{\mathrm{\Omega }}^{-1}\mathrm{c}{\mathrm{m}}^{-1}$, implying that it originates from an intrinsic Berry curvature effect stemming from Weyl nodes found in the electronic structure. These electronic structure calculations indicate the presence of nested Fermi surface pockets with nesting wave vectors like the measured magnetic ordering wave vector and the presence of Weyl nodes in proximity to the Fermi surface. We associate the incommensurate magnetic structure with the large anomalous Hall response to be the result of the combination of Fermi surface nesting and the Berry curvature associated with Weyl nodes.

We performed powder neutron diffraction experiments on a $\frac{1}{2}$ quantum magnetization plateau compound ${\mathrm{Ni}}_2{\mathrm{V}}_2{\mathrm{O}}_7$ for magnetic fields in the range 0–10 T. The incommensurate magnetic structures with the propagation vector $(k_x\sim 0.45,0,0)$ were determined at 0 T and at 6.0 K (between $T_{\mathrm{N}1}=6.7$ K and $T_{\mathrm{N}2}=5.7$ K) and 2.3 K. Consequently, the Ni1 and Ni2 moments were disordered and ordered at 6.0 K, respectively, indicating a partially disordered state. The magnetic structure of Ni2 moments was a spin density wave structure with moments ordered parallel to the $b$ axis and perpendicular to the propagation vector. Both Ni1 and Ni2 moments exhibited ellipsoidal cycloidal incommensurate magnetic structures at 2.3 K. These moments lay in the $ab$ plane. The maximum magnitudes of Ni1 and Ni2 moments [1.62(16) and 2.50(6) ${\mu }_{\mathrm{B}}$] at 2.3 K were sufficiently smaller and slightly larger than the value ($\sim 2.2{\mu }_{\mathrm{B}}$) expected from the classical picture. Further, we evaluated the field-induced magnetic moments as follows: $m_1=0.3$ and $m_2=1.9{\mu }_{\mathrm{B}}$ at Ni1 and Ni2 sites, respectively, at 10 T and 1.9 K, where the $\frac{1}{2}$ quantum magnetization plateau was observed. The results indicating both the ordered moment at 0 T and the field-induced moment at 10 T being small and large at Ni1 and Ni2 sites, respectively, were consistent with results expected in the $\text{dimer}+\text{monomer}$ model that was proposed by J. J. Cao et al. [Phys. Rev. B 106, 184409 (2022)].

We report on an extensive experimental study of the low-temperature–high-field corner of the $H\text{−}T$ phase diagram in FeSe using high-sensitivity specific heat $C$ measurements. Indeed, the superconducting gap and Fermi and Zeeman energies are surprisingly close in this compound, possibly leading to the existence of different superconducting phases as well as Lifshitz transitions in the electronic structure. The nature of this part of the phase diagram hence remains debated, and we show here that two distinct anomalies are visible in $C\left(H\right)$ (below $\sim 3$ K): a (smeared) jump at the superconducting transition and a kink in $C\left(H\right)$. This second structure lies either below (for $H$ close to the $ab$ plane) or above (for field orientations close to the $c$ direction) the superconducting transition, indicating that it is most probably related to a field-induced change in the electronic structure. Moreover, quantum oscillations are clearly observed below $\sim 2$ K, and $C\left(H\right)$ can be well described by the Lifshitz-Kosevich formula for fields both above and below the kink (with an effective mass $m^{*}\sim 4m_e$ and a frequency $F\sim 200$ T, in good agreement with the values previously inferred from magnetotransport measurements for the hole sheet).

We carry out a detailed study of the role of electronic interaction on $p$ oxygen orbitals in a Mott insulator oxide (${\mathrm{UO}}_2$) and a charge transfer oxide (${\mathrm{TiO}}_2$). First, we calculate values of effective interactions $U_{ff}, U_{pp}$, and $U_{fp}$ in ${\mathrm{UO}}_2$ and $U_{dd}, U_{pp}$, and $U_{dp}$ in ${\mathrm{TiO}}_2$. Second, we analyze the role of electronic interactions $U_{pp}$ on $p$ orbitals of oxygen in spectral and structural properties. Finally, we show that this role depends strongly on the definition of correlated orbitals and that using Wannier functions leads to more physical results for spectral and structural properties.

Motivated by the observation of topological states in $AB$-stacked ${\mathrm{MoTe}}_2/{\mathrm{WSe}}_2$, we construct the symmetry-adapted Wannier states and tight-binding model for the quantum spin Hall bands in this system. Our construction is based on the symmetry analysis of Bloch states obtained from the continuum moiré Hamiltonian. For model parameters extracted from first-principles calculations, we find that the quantum spin Hall bands can be described by a tight-binding model defined on a triangular lattice with two Wannier states per site per valley. The two Wannier states in a given valley have the same Wannier center but different angular momenta under threefold rotation. The tight-binding model reproduces the energy spectrum and accurately describes the topological phase transition induced by the out-of-plane displacement field. Our study sheds light on the topological states in moiré transition metal dichalcogenides bilayers and provides a route to addressing the many-body physics in $AB$-stacked ${\mathrm{MoTe}}_2/{\mathrm{WSe}}_2$.

We argue that strain engineering is a powerful tool that may facilitate the experimental realization and control of topological phases in laser-driven two-dimensional (2D) ferromagnetic systems. To this extent, we show that by applying a circularly polarized laser field to a 2D honeycomb ferromagnet that is uniaxially strained in either the zigzag or armchair direction, it is possible to generate a synthetic Dzyaloshinskii-Moriya interaction tunable by the intensity of the applied electric field, as well as by the magnitude of applied strain. Such deformations enable transitions to phases with the opposite sign of the Chern number, or to trivial phases. These are basic results that could pave the way for the development of a new field of strain-engineered topological spintronics.

Rapid developments for topological materials have promoted the search for topological transport in the fields of condensed-matter physics and materials science. However, topological network transport, proposed in twisted bilayer graphene and soon after being explored in other two-dimensional materials, is still elusive despite extensive experimental efforts. Here, we implemented on-chip phononic crystal networks based on a network unit cell with six channels consisting of triangular prisms on a silicon substrate arranged in a honeycomb array. The topological network bulk transport in the gap of the bulk states of the original phononic crystal and the network edge transport in the gap of the network bulk states were visualized directly. These results offer a controllable platform for exploring topological transport in networks and may enable the realization of on-chip microultrasonic devices, such as splitters, filters, and signal processing in a monolithic elastic network.

Several recent works have introduced highly compact representations of single-particle Green's functions in the imaginary time and Matsubara frequency domains, as well as efficient interpolation grids used to recover the representations. In particular, the intermediate representation with sparse sampling and the discrete Lehmann representation (DLR) make use of low rank compression techniques to obtain optimal approximations with controllable accuracy. We consider the use of the DLR in dynamical mean-field theory (DMFT) calculations, and in particular show that the standard full Matsubara frequency grid can be replaced by the compact grid of DLR Matsubara frequency nodes. We test the performance of the method for a DMFT calculation of ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$ at temperature $50\mathrm{K}$ using a continuous-time quantum Monte Carlo impurity solver, and demonstrate that Matsubara frequency quantities can be represented on a grid of only 36 nodes with no reduction in accuracy, or increase in the number of self-consistent iterations, despite the presence of significant Monte Carlo noise.

Coherent tunneling processes of multiple Cooper pairs across a Josephson junction give rise to high harmonics in the current phase relation. In this work, we propose and study Josephson junctions based on semiconductor–superconductor–ferromagnetic insulator heterostructures to engineer nonsinusoidal current-phase relations. The gate-tunability of the charge carriers' density in the semiconductor, together with the adjustable magnetization of the ferromagnetic insulator, provides control over the content of the supercurrent harmonics. At finite exchange field, hybrid junctions can undergo a $0 – \pi$ phase transition, resulting in a supercurrent reversal. Close to the transition, single-pair tunneling is suppressed and the current-phase relation is dominated by the second-harmonic, indicating transport primarily by pairs of Cooper pairs. Finally, we demonstrate that noncollinear magnetization or spin-orbit coupling in the leads and the junction can lead to a gate-tunable Josephson diode effect with efficiencies of up to $\sim 30\%$.

Engineering a layer of nitrogen-vacancy (NV) centers on the tip of a diamond anvil creates a multipurpose quantum sensor array for high-pressure measurements, especially for probing the magnetic and superconducting properties of materials. Expanding this concept above 100 GPa appears to be a substantial challenge. We observe that deviatoric stress on the anvil tip sets a limit at 40–50 GPa for practical magnetic measurements based on the optically detected magnetic resonance (ODMR) of NV centers under pressure. We show that this limit can be circumvented up to at least 130 GPa by machining a micropillar on the anvil tip to create a quasihydrostatic stress environment for the NV centers. Improved hydrostaticity is quantified using the pressure dependence of the diamond Raman shift, the NV ODMR dependence on applied magnetic field, and NV photoluminescence spectral shift. This paves the way for the reliable use of NV microsensing at pressures above 100 GPa.

The nature of the 1/9-magnetization plateau of the spin-$\frac{1}{2}$ kagome Heisenberg antiferromagnet remains controversial due to the exotic physical properties and high complexity induced by the geometrical frustration. Instead of a ${\mathbb{Z}}_3$ quantum spin liquid revealed on a cylinder, we show on an infinite-size lattice that the 1/9 plateau can be described by a valence bond crystal (VBC) that breaks spatial translational invariance. Consistent results are achieved by two accurate tensor network methods, namely the full-update infinite projected-entangled pair states and the projected-entangled simplex states. The VBC exhibits an hourglass pattern with $\sqrt{3}\times \sqrt{3}$ spatial symmetry, demonstrated by magnetizations, bond energies, and three-body correlators. The spatial inversion symmetry in the $\sqrt{3}\times \sqrt{3}$ VBC is instantly broken with the presence of the difference between the coupling strengths in the up and down triangles, suggesting the existence of gapless excitations. The gapless nature of the 1/9 plateau is further indicated by the scaling behaviors of the entanglement entropy and the correlation length, which indicate a $c=1$ conformal field theory.

The anomalous Hall effect is generally treated to originate from the Berry curvature of the band structure and scattering of the impurities, which is mainly attributed to the skew scattering and side jump for a single scattering source. In this Letter, using a first-principles-based scattering wave-function approach, we find an abnormal scaling law of the anomalous Hall effect in $L{1}_2$-type ${\mathrm{Mn}}_{3}X$ ($X=\text{Ir}$, Pt, Rh). Different from current conventional skew scattering, side jump, and Berry curvature contributions, this abnormal scaling law is demonstrated to come from a two-center scattering (TCS) contribution. Moreover, the corresponding anomalous Hall conductivity can be as large as ${\sigma }^{\mathrm{H}}\simeq 5\times {10}^4{\left(\mathrm{\Omega }\mathrm{cm}\right)}^{-1}$ in ${L1}_2$-type ${\mathrm{Mn}}_3\mathrm{Ir}$ at low temperature, which is two orders of magnitude larger than the current Berry curvature calculations, indicating that the TCS contribution dominates the anomalous Hall effect in noncollinear antiferromagnetic metals.

With the advent of x-ray free electron lasers (XFELs), ultrafast laser excitation leading to nonequilibrium states has become an important way to investigate thermal processes. Here, we use ultrafast x-ray diffraction in an XFEL pump-probe experiment to examine the lattice dynamics of 300 nm polycrystalline palladium (Pd) thin films. In our experiment, at higher laser fluence levels, we directly observe a compression effect launched from the surface skin layer heated by the optical pulse which propagates across the film over the first tens of picoseconds. After that, a lattice expansion becomes dominant, followed by a quasi-steady state lasting into the nanosecond timescale. For the lowest fluence, the compression component is not detected, indicating that the dynamics is highly dependent on the laser power. Our results shed light on the dynamics behind ultrafast processes in metallic Pd, and they can be extended to different crystalline structures.

We describe a simple and transparent physical model for local acoustic resonances and their interactions in three-dimensional phononic crystals. The widely quoted point-mass-in-a-box representation of acoustic resonators is systematically generalized to an extended rigid body connected to massive springs, exhibiting multiple coupled local resonances. Millimeter-sized acoustic resonators over the audible frequency range typically consist of dense cores coupled to stiff shells through elastically soft material. When the local resonator is small compared to the acoustic wavelength, an elastostatic equilibrium approximation yields closed-form rational functions for its frequency-dependent, effective mass and moment of inertia. Our representation allows intuitive and quantitative analyses of the coupled acoustic modes of lattices of interacting resonators. The existence and the frequency range of local resonance band gaps are predicted by the concurrence of negative effective mass and moment of inertia. A large local resonance gap may occur in spectral proximity to a distinct gap arising from Bragg scattering. The band structure and density of states are determined by solving computationally inexpensive $6\times 6$ matrix eigenvalue equations. These agree with the exact band structures obtained by finite-element method within $3.71\%$, $2.32\%$, and $2.38\%$ errors for the simple cubic, body-centered cubic, and face-centered cubic arrangements of the resonators, respectively. Our model enables precise design of locally resonant phononic crystals with large dual band gaps spanning a significant fraction of the audible spectrum. By increasing the mass contrast between the core and the shell in spherical resonators, we demonstrate, using a specific phononic crystal, a local resonance band gap with $126.7\%$ gap-to-midgap ratio. Our model is further extended to a lattice of dumbbell-shaped resonators, resulting in a dense collection of flat bands over a narrow, predetermined frequency range.

The magnetic properties of $\mathrm{Pt}\text{/}{Co}_{1-x}{\mathrm{Lu}}_x\text{/}\mathrm{Pt}$ thin films have been investigated. For an alloy thickness of 3 nm, the saturation magnetization linearly decreases from 830 kA/m to 400 kA/m for $x$ varying between 18% and 40%, including the proximity-induced moment in platinum. Furthermore, we show that ${\mathrm{Co}}_{1-x}{\mathrm{Lu}}_x$ alloys 3 nm thick thin films have a perpendicular magnetic anisotropy for a concentration ranging between 25% and 40%. A single femtosecond laser shot leads to a demagnetized state with a domain size that increases with the decrease of saturation magnetization. Patterning the layer into dots leads to a single domain structure that can be fully reversed using a single laser pulse. The statistics and the origin of the nondeterministic reversal are discussed based on the atomistic model.

The three-dimensional antiferromagnet ${\mathrm{Cu}}_3{\mathrm{TeO}}_6$ has recently drawn significant attention due to the coexistence of Dirac and triply degenerated magnons. Herein, we report that ${\mathrm{Cu}}_3{\mathrm{TeO}}_6$, with cubic symmetry, exhibits novel spin-driven ferroelectric polarization ($P$) with a strong linear magnetoelectric (ME) coupling effect by comprehensive measurements in magnetization and electric polarization. The magnetic field ($H$)-induced polarization along x-, y-, and $z$-axes emerges below $T_{\mathrm{N}}\sim 61\mathrm{K}$, indicative of intrinsic coupling between magnetism and ferroelectricity in this cubic lattice. Our results reveal nine nonvanished components of a ME tensor, while only the $P_x \left(H//z\right), P_y \left(H//x\right)$, and $P_z \left(H//y\right)$ components display a remarkable linear response to $H$. In particular, we observe six ME states—namely, $(\pm P_x,\pm M_z), (\pm P_y,\pm M_x)$, and $(\pm P_z,\pm M_y)$—that can be generated by applying an external magnetic field in a specific direction, and thus makes ${\mathrm{Cu}}_3{\mathrm{TeO}}_6$ a very appealing prototype in multifunctional applications. Our results point toward ${\mathrm{Cu}}_3{\mathrm{TeO}}_6$ as a new, linear ME material and may pave a way to exploring the rich ME response in the presence of a Dirac magnon in a highly symmetric crystal structure.

Over the past years, one witnesses a growing interest in flat band (FB) physics which has become a playground for exotic phenomena. In this study, we address the FB superconductivity in one-dimensional stub chain. In contrast to the sawtooth chain or the Creutz ladder, for a given strength of the attractive electron-electron interaction, the stub chain allows the tuning of the real space spreading of the FB eigenstates (quantum metric or QM). We study in detail the interplay between the interaction strength and the mean value of the QM $\langle g\rangle$ on the pairings and on the superfluid weight $D_s$. Our calculations reveal several interesting and intriguing features. For instance, in the weak coupling regime, $D_s$ with respect to $\langle g\rangle ,$ exhibits two different types of behavior. Despite the fact that the pairings differs drastically, $D_s$ scales linearly with the QM only when its $\langle g\rangle$ is large enough (small gap limit). On the other hand, when the QM is of small amplitude an unusual power law is found, more precisely $D_s\propto {\langle g\rangle }^{\nu }$, where $\nu \to 2$ in the limit of large single particle gap. In addition to the numerical calculations, we have provided several analytical results which shed light on the physics in both the weak and strong coupling regime. Finally, we have addressed the impact of the thermal fluctuations on the superfluid weight.

It is known that strong disorder in closed quantum systems leads to many-body localization (MBL), and that this quantum phase can be destroyed by coupling to an infinitely large Markovian environment. However, the stability of the MBL phase is less clear when the system and environment are of finite and comparable size. Here, we study the stability and eventual localization properties of a disordered Heisenberg spin chain coupled to a finite environment, and extensively explore the effects of environment disorder, geometry, initial state, and system-bath coupling strength, using the steady-state value of magnetization as a probe. Focusing on nonequilibrium dynamics and steady-state properties, our results indicate that within system sizes amenable to exact diagonalization, a strongly localized system interacting in a junction configuration retains remnant information on its initial state at long times despite coupling to a finite ergodic environment. In contrast, in a ladder configuration, strong dependencies on the initial state and coupling strength are observed, which can lead to either the loss or retention of information. Finally, we highlight and discuss discrepancies that can arise when similar methodologies are employed to infer localization or thermalization, revealing the need for careful interpretation.