Anisotropic magnetoresistance (AMR) has a crucial feature for developing highly sensitive sensors and innovative memory devices. While extensively studied in bulk materials, AMR effects in these materials are typically weak. Recent advancements indicate that two-dimensional (2D) van der Waals magnetic materials possess unique magnetic properties, potentially including significant AMR characteristics. In this study, we utilize density functional theory and the Boltzmann transport equation to investigate AMR in magnetic monolayers $\mathrm{CrP}{X}_3$ $(X=\mathrm{S}, \mathrm{Se}, \mathrm{Te})$. Our findings reveal a substantially large AMR in these 2D magnetic compounds. This enhancement is attributed to magnetization (M)-dependent spin-orbit coupling (SOC), arising from the broken symmetry between in-plane and out-of-plane orientations. This results in significant M-dependent band splitting and subsequent variations in electron velocity. Additionally, we find that the M-dependent SOC is significantly enhanced by increasing the atomic number of the chalcogen X in $\mathrm{CrP}{X}_3$, achieving an exceptional 150% AMR in ${\mathrm{CrPTe}}_3$. Furthermore, our study demonstrates that AMR can be effectively modulated by applying biaxial strain, resulting in a twofold increase with a 4% strain. These findings propose a unique approach to enhancing 2D-based AMR spintronic devices, making a substantial contribution to the field.

The proximity-induced superconducting (S) correlations in ferromagnetic (F) layers of planar S/F hybrids are shown to be responsible for the appearance of a nonlinear interaction between the magnetic moments of the F layers. This interaction originates from the combined influence of the orbital and exchange phenomena and can result in the spontaneous formation of noncollinear magnetic states in these systems. The proposed nonlinear coupling mechanism and resulting changes of magnetic textures are crucial for the design of the superconducting spintronics devices exploiting the long-range spin-triplet proximity effect.

Silica is a fundamental component of planetary interiors, and the knowledge of its high-pressure polymorphs is essential for constructing planetary models. The pyrite silica has been synthesized in static compression with diamond anvil cells, however, it has never been observed in dynamic compression experiments, despite enormous efforts. Here, based on a machine-learning interatomic potential fitted from first-principles calculations, we perform multimillion-atom molecular dynamic simulations to study the dynamics compression pathways to obtaining the pyrite phase starting from stishovite. We find that the pyrite phase can be achieved through shock compressions along three directions of stishovite: [100], [110], and [001]. Our study reveals the orientation-dependent phase transition of stishovite during shock compression, with displacive phase transition occurring along the [100] direction and diffusive phase transformation along [110] and [001] directions. Our research provides insight into obtaining pyrite-type silica from stishovite through dynamic compression and elucidates the microscopic transformation mechanisms involved.

Machine learning potentials (MLPs) have become indispensable for conducting accurate large-scale atomistic simulations and for the efficient prediction of crystal structures. Polynomial MLPs, defined by polynomial rotational invariants, have been systematically developed for a wide range of elemental, alloy, and ionic systems. This study introduces a highly efficient and robust methodology for enumerating globally stable and metastable structures utilizing polynomial MLPs. To develop MLPs that are sufficiently robust for structure enumeration, an iterative process involving random structure searches and subsequent updates to the MLPs is employed. This methodology has been systematically applied to elemental systems such as As, Bi, Ga, In, La, P, Sb, Sn, and Te, where numerous local minima present significant competition with the global minimum in terms of energy. The proposed approach facilitates robust global structure searches and structure enumerations by markedly accelerating the search process and expanding the search space.

The determination of Lande's $g$ factor and the damping constant is central to extracting crucial information about the spin-spin and spin-orbit interactions in magnetically ordered systems. In insulating compounds based on $3d$ elements, the spin-orbit interaction can be effectively probed by investigating the ground state of the corresponding free $3d$ ion within the crystalline environment. For metallic systems, the problem is nontrivial because of additional band structure effects. Here, we investigate the anisotropic magnetization dynamics in bulk single-crystalline ${\mathrm{Fe}}_5{\mathrm{GeTe}}_2$, a van der Waals 2D itinerant ferromagnet at room temperature, using broadband ferromagnetic resonance spectroscopy. We demonstrate the absence of intrinsic anisotropy of magnetization damping close to room temperature, suggesting diminished role of spin-orbit interaction. However, there is a sizable anisotropy in the Lande's $g$ factor near room temperature, which is attributed to anisotropic critical spin fluctuations.

We analyze the temperature evolution of the anomalous magnetic spectrum of the spin-1/2 triangular quantum Heisenberg antiferromagnet, which is proximate to a quantum phase transition leading to a spin-liquid phase. Recently, its low-energy excitations have been identified with two-spinon bound states, well defined in an ample region of the Brillouin zone. In this work, we compute the thermal magnetic spectrum within a Schwinger boson approach, incorporating Gaussian fluctuations around the saddle-point approximation. In order to account for a finite Néel temperature $T_N$, we incorporate an exchange interaction between triangular layers. As temperature rises, the dispersion relation of the two-spinon bound states, representing single-magnon excitations, remains unchanged but becomes mixed with the thermally activated spinon continuum. Consequently, a crossover occurs at a temperature $T^{*}\simeq 0.75T_N$, defining a terminated Goldstone regime between $T^{*}$ and $T_N$, where only the magnons close to the Goldstone modes survive as well-defined excitations, up to the Néel temperature. Our results support the idea that the fractionalization of magnons near a transition to a disordered phase can be extended to more realistic quasi-two-dimensional frustrated antiferromagnets.

We find analytic expressions for the damping- and field-like spin-transfer torques generated at the interface between two fully spin-polarized ferromagnetic metals (half-metals). The proposed one-dimensional model shows that in the case of nonidentical ferromagnets the field-like torque can exhibit linear proportionality to the current, as opposed to the quadratic dependence found for identical materials. The ratio of damping- and field-like torques is then well defined in the small current limit. When viewed as a function of the angle between the ferromagnet's magnetizations, it exhibits a prominent peak that is found to coincide with the transition from Ohmic to tunneling electron transport through the interface. We conjecture that transition between two transport regimes is indeed the physical cause of the sharp feature in the torques' ratio. This suggests that a qualitatively similar peak will be found in the more realistic models as well.

The intricate interplay between frustration and spin chirality, induced by the Dzyaloshinskii-Moriya interaction, holds promise for unveiling novel phases in frustrated quantum magnets. This study investigates the ground state phase diagram of the spin-$\frac{1}{2}$ square lattice $J_1\text{−}{J}_2$ model upon incorporation of the chiral interaction $J_{\chi }$. Employing exact diagonalization (ED) with full lattice symmetries, we analyze the phase evolution as a function of $J_2$ at fixed $J_{\chi }$, utilizing highly symmetric energy levels. Critical level crossings and ground state fidelity susceptibility (FS) techniques aid in pinpointing phase boundaries: Magnetic to nonmagnetic phase transitions are identified through critical level crossings between gapless magnetic excitations and quasidegenerate ground states of nonmagnetic phases. Direct transitions between two nonmagnetic phases are characterized by FS peaks due to avoided ground state level crossing. Based on these observations, we identify an anticipated chiral spin liquid (CSL) state and an adjacent nematic spin liquid (NSL) phase within a significant range of $J_{\chi }$, demarcated by a nearly vertical boundary line at $J_2\approx 0.65$. This critical line terminates at the lower boundary in $J_{\chi }$ of a magnetic ordered chiral spin solid phase, which gains prominence with increasing $J_{\chi }$ from both CSL and NSL phases. The topological nature of the CSL is confirmed using the modular $\mathcal{S}$ matrix of minimally entangled states on a torus and the entanglement spectra of even and odd sectors on a cylinder, employing ED and $\mathrm{SU}\left(2\right)$-symmetric density matrix renormalization group method, respectively. Furthermore, a comprehensive discussion on the nature of the NSL is provided, exploring aspects such as ground state degeneracy, local bond energy landscape, and singlet and triplet gaps on various tori, offering substantial evidence supporting the nematic nature of the NSL.

Trillium lattices formed by corner-shared triangular units are the platform for magnetic frustration in three dimensions. Herein, we report structural and magnetic properties of the Cr-based ($S=3/2$) double trillium lattice material ${\mathrm{KBaCr}}_2{\left({\mathrm{PO}}_4\right)}_3$ studied by x-ray diffraction, dc and ac magnetization, heat capacity, thermal conductivity, and ${}^{31}\mathrm{P}$ nuclear magnetic resonance (NMR) measurements complemented by density-functional band-structure calculations. Magnetization, heat capacity, and ${}^{31}\mathrm{P}\mathrm{NMR}$ measurements reveal the magnetic transition at $T_{\mathrm{N}1}\simeq 12.5\mathrm{K}$ in zero field followed by another transition ($T_{\mathrm{N}2}$) at low temperatures in weak applied fields. The ${}^{31}\mathrm{P}$ spin-lattice relaxation rate in the ordered state follows the $T^3$ behavior indicative of the two-magnon Raman process. The spin lattice of ${\mathrm{KBaCr}}_2{\left({\mathrm{PO}}_4\right)}_3$ comprises two crystallographically nonequivalent ferromagnetic sublattices that are coupled antiferromagnetically, thus eliminating frustration in this trillium network and leading to weak ferromagnetism in the vicinity of $T_{\mathrm{N}1}$.

The magnetic behavior of the $\left(\mathrm{Sc},\mathrm{Nb}\right)\mathrm{F}{\mathrm{e}}_2$ series of intermetallic compounds was thoroughly investigated in the ordered ferromagnetic state as well as in the paramagnetic regime. The magnetic moment of the Fe sublattice was determined from 4 K up to the magnetic ordering temperature while the analysis of the paramagnetic state yielded the determination of the effective paramagnetic moment and Curie-Weiss temperature. The number of carriers was estimated below and above the Curie point so as to discuss the degree of itinerancy of Fe magnetism in the $\left(\mathrm{Sc},\mathrm{Nb}\right)\mathrm{F}{\mathrm{e}}_2$ system. The experimental results were analyzed in the frame of Kuz'min's model describing the temperature dependence of the spontaneous magnetization, and Takahashi's theory of spin fluctuations. It is shown that both Curie temperature and paramagnetic Curie-Weiss temperature decrease linearly upon increasing Nb content. The longitudinal spin fluctuations progressively increase for the richest Nb compositions, by contrast, transverse spin fluctuations dominate for the parent compound $\mathrm{ScF}{\mathrm{e}}_2$. Furthermore, a reduction in ferromagnetic interactions upon Nb for Sc substitution is observed, resulting in an evolution from a short-range ferromagnet for $\mathrm{ScF}{\mathrm{e}}_2$ to systems with competing exchange interactions for Nb-rich composition. Nb-rich $\left(\mathrm{Sc},\mathrm{Nb}\right)\mathrm{F}{\mathrm{e}}_2$ compounds evolve progressively toward the weakly ferromagnetic limit. Spin-fluctuation parameters have been determined from magnetic measurements using Takahashi's model. We report an evolution from mostly localized magnetic character of Fe moments to a strongly delocalized one upon increasing the Nb content along the $\mathrm{S}{\mathrm{c}}_{1-x}\mathrm{N}{\mathrm{b}}_x\mathrm{F}{\mathrm{e}}_2$ series of compounds. In the composition range $0 \le x \le 0.22$ the degree of itinerancy is nearly constant, whereas for $x>0.22$ it is remarkably dependent upon the Nb concentration.

The presence of multiple orders in strongly correlated electronic materials like the cuprate superconductors, coupled with spatial inhomogeneity, poses a challenge to the interpretation of spectroscopic data taken on them. Here, we present a technique that directly acknowledges these orders and inhomogeneities and extracts statistically significant features from such data. Applying this technique to scanning tunneling spectroscopy measurements from single and bilayer cuprates spanning a wide doping range, we peer through local inhomogeneities and identify a gaplike feature that breaks translational and rotational symmetries and varies periodically in a fourfold pattern. This identification of spectral features aligns well with theoretical predictions of spatially modulated pair density.

We study high harmonic generation in altermagnetic metals with and without spin-orbit coupling. The altermagnetism manifests itself in the magnetic field dependence of the low harmonics associated with intraband dynamics. Spin-orbit coupling leads to additional higher-energy peaks and plateau structures originating from interband transitions. While the pure altermagnet or spin-orbit system exhibits no circular dichroism in the high harmonic response, an altermagnetic system with spin-orbit coupling shows such a dichroism. We also analyze the spin currents and their high harmonic spectrum.

Bound states in the continuum (BICs) are spatially localized states whose eigenvalues are situated within the continuum of extended states. Recent research has demonstrated that the interaction between BICs and the non-Hermitian skin effect (NHSE) can give rise to an extended state in a localized continuum (ELC), which is essentially the inverse of the BICs. Here, we propose and experimentally demonstrate a very general and simple approach for the generation of the ELC in a mirror-stacking system. This approach allows the Hamiltonian of the bilayer system to be decoupled into two topological subspaces. Upon tuning the interlayer coupling, the BICs are realized when the topological bound states spectrally overlap with the bulk band. The ELC arises with the introduction of the NHSE, which not only transforms all bulk modes into skin modes but also concurrently delocalizes the bound state. As a representative example, we experimentally realize the ELC in a mirror-stacked non-Hermitian Su-Schrieffer-Heeger electric circuit. Our findings are expected to expand the research significance of NHSE and ELCs.

Using the density functional theory plus dynamical mean-field theory method, we revisit the pressure-temperature phase diagram of the prototypical correlated insulator NiO. We study the pressure-induced evolution of the electronic structure, magnetic state, and exchange couplings of the antiferromagnetic (AFM) phase of NiO. We calculate the ordered magnetic moments and static magnetic spin susceptibility of the Ni $3d$ states of NiO, which allow us to determine the pressure dependence of the Néel temperature $T_N$. We note that the long-range magnetism has no significant effects on the valence band photoemission spectra of NiO under moderate compressions, implying the importance of correlation effects to explain the insulating state of NiO. Upon compression, we observe a crossover from a charge transfer to the Mott-Hubbard insulating character of the insulating gap, with a predominant contribution from the majority Ni $e_g$ states near the Fermi level. The insulating state of AFM NiO is found to be stable up to a high compression $\sim 0.4V_0$ (assuming the cubic $B1$ crystal structure of NiO). It is categorized as a correlation-assisted Slater-type insulator, implying the importance of long-range magnetic ordering. In fact, the paramagnetic phase of NiO at such high compression is found to be metallic, characterized by strong delocalization of the Ni $3d$ states. The calculated $T_N$ exhibits a nonmonotonic behavior upon compression, with a maximum associated with the crossover from Mott localized (strong coupling) to itinerant moment regimes, in qualitative agreement with the phase diagram of the half-filled single-band Hubbard model. We point out the importance of the nonlocal correlation effects to explain the magnetic properties of NiO.

We report the observation of an electronic reconstruction in dimensionally controlled ruthenate heterostructures synthesized by pulsed laser deposition. High structural and electronic quality of superlattices comprised of a single ${\mathrm{SrRuO}}_3$ layer inter-spaced with varying thicknesses of insulating ${\mathrm{SrTiO}}_3$ layers was verified by reflection high energy electron diffraction, atomic force microscopy, x-ray diffraction, reciprocal space mapping, and x-ray absorption spectroscopy. X-ray absorption spectroscopy evidences a confinement-driven evolution of the Ru electronic configuration from the $d^5\underline{L}$ to the $d^4$ state. Significant increases of the spin-orbit coupling are observed in connection with the configuration changes supporting recent works identifying large enhancement of the magnetic anisotropy. The growth of high quality two-dimensional confined ruthenate layers under precisely controlled environments highlights the potential to directly manipulate interlayer coupling and selectively perturb the electronic state in ruthenates in analogy to superconducting ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$.

We propose an SSH-BCS-Hubbard chain model and theoretically study the interplay of topology and interaction therein. We obtain the exact solution of the model at the symmetric point. The exact solution reveals that the Hubbard interaction induces $Z_2$ symmetry breaking, which leads to the coexistence and competition of antiferromagnetic order and $\eta$-pairing order. The interaction splits the zero-energy states into in-gap states and destroys the symmetry-protected topological state of the SSH-BCS chain. However, the symmetry analysis reveals that the interacting topological state can exist for small Hubbard interaction and dimerization. The topological phase transition of the perturbed SSH-BCS-Hubbard is studied via the spectral $Z_2$ topological invariant. Our study uncovers a stable interacting topological state coexisting with symmetry-breaking induced intertwined orders.

Nickel oxide superconductors offer an alternative playground for understanding the formation of Cooper pairs in correlated materials such as the famous cuprates. By studying the $\mathrm{L}{\mathrm{a}}_{n+1}\mathrm{N}{\mathrm{i}}_n{\mathrm{O}}_{2n+2}$ phase diagram on the basis of hybrid and spin-polarized density functional theory simulations, we reveal the existence of charge and bond ordered (CBO) insulating phases that are quenched by doping effects, ultimately resulting in a metallic phase at the $n=5$ member. Nevertheless, the phonons associated with the CBO identified in the phase diagram remain sufficiently large to mediate Cooper pairs in $\mathrm{L}{\mathrm{a}}_6\mathrm{N}{\mathrm{i}}_5{\mathrm{O}}_{12}$, yielding a computed critical temperature between $T_c=11$ and 19 K consistent with the 13 K observed experimentally in $\mathrm{N}{\mathrm{d}}_6\mathrm{N}{\mathrm{i}}_5{\mathrm{O}}_{12}$. Hence, an electron-phonon mechanism cannot be ruled out in nickelates. Finally, in order to identify the superconducting mechanism, extracting the relevant instabilities in the doping phase diagram of superconductors appears critical.

The two-dimensional $d$-electron system formed at the $\mathrm{LaAlO}{}_3/\mathrm{SrTiO}{}_3$ (LAO/STO) interface exhibits intriguing gate-tunable magnetism, superconductivity, and Rashba spin-orbital coupling (RSOC), originating from electronic correlations and multiorbital effects. Here, we theoretically study the interfacial Kondo effect arising from the exchange coupling between the localized $d_{xy}$ state induced by defects and itinerant $t_{2g}$ orbitals in the presence of $k$-linear/cubic-dependent RSOC. By analyzing the temperature-dependent magnetic susceptibility, we show that both linear and cubic RSOC induced hybridization between itinerant $d_{xy}$ and $d_{xz/yz}$ orbitals around the Lifshitz transition point, enhances the Kondo screening of the localized magnetic moment. Significant pronounced orbital hybridization near the $d_{xy}\text{−}{d}_{xz/yz}$ crossing region leads to the enhancement of the Kondo effect depending on the position of the Fermi level, which can be tuned by an applied electric gate voltage. Our results propose a tunable scheme to explore the multiorbital effects and electronic correlations at the LAO/STO interface.