Shallow nitrogen-vacancy (NV) centers in diamond are useful for near-surface sensing, but the negatively charged state ${\mathrm{NV}}^{-}$ is often difficult to stabilize close to the surface. Here we study the depth dependence of NV formation and charge-state stability in nitrogen-implanted diamond using spatially resolved photoluminescence (PL) spectroscopy, dynamic secondary ion mass spectrometry (D-SIMS), stopping and range of ions in matter (SRIM) simulations, and first-principles density functional theory (DFT) calculations. Although the near-surface region contains a higher nitrogen concentration, its NV-related PL emission is much weaker than that from the shallow subsurface region. This behavior shows that nitrogen incorporation alone is not sufficient to explain the observed ${\mathrm{NV}}^{-}$ stability. The depth profiles obtained from D-SIMS and SRIM support the intended difference between the near-surface and shallow-subsurface implantation regions. To examine the possible role of residual implantation damage, we further compare ideal NV and carbon-interstitial-related NV (NV-int) defect models by DFT. The interstitial-related defect model gives an upward shift of the $\varepsilon \left(0/-\right)$ transition level by about 3.23 eV. Charge-density-difference and density-of-states analyses further reveal local charge redistribution and reconstruction of defect-related electronic states around the NV center. These changes establish a microscopic explanation for the reduced stability of ${\mathrm{NV}}^{-}$ in defect-rich near-surface regions. Our results indicate that shallow NV engineering should focus not only on nitrogen placement, but also on reducing residual implantation-induced defects.

The three-dimensional (3D) magnet ${\mathrm{KBaFe}}_2$(${\mathrm{PO}}_4{)}_3$ hosts an effective tetratrillium spin lattice of ${\mathrm{Fe}}^{3+}$ ($S=5\text{/}2$) ions, offering a prototypical platform to study frustration-driven phenomena in 3D. Through magnetization, specific heat, ${}^{31}\mathrm{P}$ nuclear magnetic resonance (NMR), and muon spin relaxation ($\mu \mathrm{SR}$) experiments, supported by first-principles calculations, we uncover an unconventional ground state. Despite strong antiferromagnetic interactions with a large Curie-Weiss temperature ${\theta }_{\mathrm{CW}}=-70\left(2\right)\mathrm{K}$, no magnetic long-range order is observed down to 30 mK. Below $T^{*}\simeq 3.5\mathrm{K}$, the NMR linewidth becomes nearly field independent and the spin-spin relaxation rate $1/T_2$ saturates, accompanied by a two-component relaxation in the transverse nuclear magnetization $M_{xy}$. The latter indicates the emergence of short-range dynamical correlations, which was further corroborated by a robust and field-insensitive broad maximum in specific heat. In $\mu \mathrm{SR}$, we detect neither a static internal field nor spin freezing; instead, the spins remain dynamic down to 30 mK and the asymmetry curves are best described by two coexisting dynamic relaxation channels: a dominant fast (sporadic) channel and a slower Markovian component. Their differing weights and fluctuation rates suggest microscopic inhomogeneity in spin dynamics. These persistent low-temperature spin fluctuations are found to be intrinsic to the 3D frustrated tetratrillium geometry, exemplifying ${\mathrm{KBaFe}}_2$(${\mathrm{PO}}_4{)}_3$, a rare 3D antiferromagnet with a classical spin that fosters unconventional dynamics.

A periodically driven Fermi gas coupled to a simple boson bath reaches a nonequilibrium steady-state occupation with sharp nonanalyticities at certain momenta. Here, we demonstrate that these nonanalyticities behave as emergent Fermi surfaces by showing that they give rise to quantum oscillations of observables with a period controlled by the effective Fermi-surface area enclosed by these nonanalyticities. However, these oscillations have several striking differences with standard equilibrium quantum oscillations. For example, they remain nonanalytic at finite temperatures, their amplitude can survive up to extremely high temperatures comparable to the frequency of the drive, and they can display nonmonotonic temperature dependence completely at odds with standard Lifshitz-Kosevich behavior.

Magnetic materials are crucial for manipulating electron spin and magnetic fields, enabling applications in data storage, spintronics, charge transport, and energy conversion; they also provide insight into fundamental quantum phenomena. In numerous applications, the interaction between electrons and lattice vibrations, known as electron-phonon coupling, can be of significant importance. In that regard, we extend the epw package to be able to interpolate the electron-phonon matrix elements combining perturbation theory and maximally localized Wannier functions. This enables the use of dense momentum grids at a reasonable computational cost when computing electron-phonon related quantities and physical properties. We validate our implementation considering ferromagnetic iron and nickel, where we explore the phonon induced mass enhancement and Eliashberg spectral function finding different importance of each spin channel for both compounds. Furthermore, we evaluate the carrier resistivity at finite temperatures for both systems, considering the role of the magnetic phase in carrier transport. Our findings indicate that in the case of Fe, the primary contributor to resistivity is electron-phonon scattering. In contrast, for Ni, electron-phonon scattering constitutes less than one-third of the resistivity, underscoring a fundamental difference in the transport properties of the two systems.

Altermagnetism is a recently proposed magnetic order that hosts zero net magnetization while exhibiting spin-split electronic bands. Rutile oxide ${\mathrm{RuO}}_2$ is one of the representative candidate materials, yet its intrinsic magnetic ground state remains highly debated in recent studies. Using density functional theory calculations, we demonstrate that epitaxial strain can activate intrinsic magnetism in ${\mathrm{RuO}}_2$ and effectively tune its local magnetic moments. This strain-driven magnetic response originates from the modified orbital hybridization and the crystal-field interactions. These findings provide a plausible explanation for the diversity of magnetic signatures observed in various experimental conditions, highlighting the critical role of lattice strain in stabilizing and tuning altermagnetism.

We present a systematic study of angular-dependent magnetization reversal in approximately 20-µm-thick epitaxial $\left({\mathrm{Bi}}_x{\mathrm{La}}_y{\mathrm{Y}}_{3-x-y}\right)\left({\mathrm{Fe}}_{5-z}{\mathrm{Ga}}_z\right){\mathrm{O}}_{12}$ garnet films having different Bi concentrations. All films exhibit robust perpendicular magnetic anisotropy and maintain very low Gilbert damping of the order of ${10}^{-4}$. By analyzing hysteresis behavior for different magnetic field orientations β, the nature of irreversible magnetization processes is studied over a wide angular range. Our results show that nucleation-dominated hysteretic reversal emerges only within a finite angular range near the out-of-plane orientation (approximately $\beta ={60}^{\circ }\text{–}{120}^{\circ }$ from in-plane orientation), whereas outside this range magnetization reversal is initiated via nonhysteretic instability. We also find that the angular range, in which nucleation processes occur, increases synchronously with the perpendicular anisotropy of our samples upon increasing their Bi concentration. The quantitative evolution of the observed nucleation field versus magnetic field angle β deviates markedly from a simple geometric projection onto the surface normal, which would be proportional to 1/sinβ. Nonetheless, we observe that the nucleation field increases as the field deviated from aligning with the surface normal for all our samples in contrast to prior observation in other material systems. Our findings demonstrate that despite the relevant perpendicular anisotropy of our samples, domain nucleation processes in thick garnet films are not governed solely by the perpendicular field components. Instead, our quantitative analysis illustrates that in-plane field components must be considered as an essential correction. These findings establish a coherent physical picture of magnetization reversal in thick garnet films for arbitrary magnetic field orientation.

Decorated square-kagome quantum antiferromagnets provide a natural setting in which strong frustration, lattice decoration, and spin-orbit-induced anisotropy compete on comparable energy scales. Here we show, within a Schwinger-boson mean-field treatment of the realistic Hamiltonian, that the coupling $J_{10}$ linking the decorating Cu(3) sites to the square-kagome backbone stabilizes the gapped saddle point, while symmetry-allowed Dzyaloshinskii-Moriya (DM) interactions systematically suppress the minimum spinon gap ${\mathrm{\Delta }}_{\mathrm{spinon}}$ and enhance the tendency toward boson softening. To establish this, we combine ab initio calculation of the DM vectors with a Schwinger-boson self-consistent mean-field treatment (SBMFT) extended to include the triplet hopping and pairing channels required by explicit spin-rotation-symmetry breaking. As a benchmark, the isotropic square-kagome Heisenberg model exhibits four competing low-energy saddle points distinguished by their Wilson-loop fluxes and by characteristic static and dynamical structure-factor fingerprints. A minimal DM perturbation does not qualitatively reshape this competing landscape, but already enhances low-energy spectral weight in the ordered saddle points. For the realistic decorated Hamiltonian, finite-size scaling of ${\mathrm{\Delta }}_{\mathrm{spinon}}$ together with momentum-resolved structure factors identifies $J_{10}$ as a control parameter for the stability of the gapped mean-field regime and shows that the full symmetry-allowed DM pattern shifts the spectrum toward lower energies. Our results indicate that, within SBMFT, ${\mathrm{Na}}_6{\mathrm{Cu}}_7{\mathrm{BiO}}_4{\left({\mathrm{PO}}_4\right)}_4{\mathrm{Cl}}_3$ lies close to a regime where the gapped saddle point becomes soft, and provide experimentally testable predictions for anisotropy-enhanced low-energy spectral weight in decorated square-kagome materials.

The $(A,B){\mathrm{Fe}}_2$-type Laves phase system is widely studied for a magnetochemical phase diagram, negative thermal expansion, and magnetocaloric effect. In this work, we develop a phase field model to theoretically investigate microstructure evolution and magnetic phase transitions in $({\mathrm{Hf}}_{1-x}{\mathrm{Nb}}_x){\mathrm{Fe}}_2$ pseudobinary alloys. Our simulations successfully capture the complex magnetic phase transitions within the system, including ferromagnetic (FM)-to-paramagnetic, ferromagnetic-to-antiferromagnetic (AFM), and antiferromagnetic-to-paramagnetic phase transitions. The phase diagram is obtained by the simulated magnetization-temperature curves and a triple point is identified at approximately $x=0.152$ and $T=313\mathrm{K}$, which shows excellent agreement with experimental data. Microstructure simulations reveal that the FM state forms a cuboidal-like domain pattern, while the AFM state exhibits a single domain. Moreover, a study of strain effects on ${\mathrm{Hf}}_{0.8}{\mathrm{Nb}}_{0.2}{\mathrm{Fe}}_2$ reveals that compressive strain suppresses the ferromagnetic state, and the FM-AFM phase transition temperature decreases by approximately 27 K per 0.1% increase in compressive strain, which is in accordance with experimental observations. This work provides theoretical insights into the magnetoelastic coupling in Laves phase alloys.

The IV-VI chalcogenides exhibit exotic electronic properties arising from their diverse crystal structures, including both two-dimensional (2D) and three-dimensional (3D) lattices, attracting broad interest for device application and fundamental research. Here we investigate the lattice-mismatched ternary selenide ${\mathrm{PbSnSe}}_2$, an alloy derived from the 3D PbSe and the 2D SnSe, under high pressure in a diamond anvil cell using low-temperature transport measurements, x-ray diffraction, and optical absorption spectroscopy. ${\mathrm{PbSnSe}}_2$ is a semiconductor at ambient conditions. It undergoes a pressure-induced metallization and becomes superconducting near 17.8 GPa, and the superconducting transition temperature $T_{\mathrm{c}}$ reaches 4.4 K at approximately $20.1\mathrm{GPa}$. The $T_{\mathrm{c}}$ was found to be suppressed monotonically under further compression. During decompression, a higher $T_{\mathrm{c}}$ was observed, reaching approximately 6.1 K when the pressure is released to approximately 15.5 GPa. The pressure-dependent properties of ${\mathrm{PbSnSe}}_2$ combine characteristics of its parent compounds SnSe and PbSe: the low-pressure behavior resembles that of SnSe with a Pnma structure and a monotonously decreasing band gap under pressure, whereas the high-pressure behavior is similar to PbSe, with a simultaneous emergence of metallization and superconductivity before the Pnma-to-CsCl phase transition. These results reveal complex structural evolution and emergent superconductivity in a 3D-2D alloy under pressure and provide insight into the versatile physics of this and related material families.

The pressure- and temperature-driven phase transition from polycrystalline graphite to diamond is investigated using molecular dynamics computer simulation. We partition the atomic coordinates into two disjoint subsets corresponding to a diminishing three-coordinate and a developing four-coordinate network. It is shown that the fractal dimension and its time evolution, as calculated from the radial distribution function “colored” for four coordinates only, tracks the transformation mechanism, capturing the growth and spatial organization of the developing domains. In particular, it reflects the increasing space-filling character and homogenization of the emerging diamondlike structure. At sufficiently high pressures and temperatures, the system consistently transforms into polycrystalline diamond, whereas at lower pressures the final structures depend sensitively on both temperature and initial microstructure, leading to greater variability in the fractal dimension. Additionally, we demonstrate that the transformation to four-coordinate sites leads to a percolation transition, which, compared to a simple hard sphere null model, occurs at a significantly lower threshold, highlighting the role of the interatomic potential in correlating network connectivity. These results demonstrate that the fractal dimension may provide a simple and robust metric for tracking topological changes during phase transitions in polycrystalline solids or other phenomena that may be characterized as domain growth.

Fermi surface nesting is key to understanding the origin of the itinerant antiferromagnetic spin density wave in chromium. This magnetic order is accompanied by a charge density wave, and both density waves disappear above the critical pressure $P_c\approx 10$ GPa at low temperatures, defining a quantum critical point. Whether this pressure-induced quantum phase transition is accompanied by a phonon instability remains an open question. Here, we use inelastic x-ray scattering to track the room-temperature acoustic phonon dispersions at pressures up to $P=15.6$ GPa, well above $P_c$. We focus on the Kohn anomalies near the $H$ and $N$ points of the Brillouin zone, with the $H$ point anomaly lying close to the incommensurate spin density wave ordering vector. The phonon branches harden smoothly under pressure, while the positions and wave-vector extents of both anomalies remain essentially unchanged across $P_c$, with no additional critical softening. Ab initio calculations likewise show that Fermi surface nesting remains robust above $P_c$. These results indicate that the pressure-induced quantum phase transition is not driven by a phonon instability and support a primarily spin density wave driven mechanism in presence of a robust Kohn anomaly.

We investigate the ground-state phase diagram of the spin-1 Kitaev–Heisenberg (KH) chain in the presence of uniaxial single-ion anisotropy $D_z$ using the density-matrix renormalization-group method. The relative strength of the Heisenberg and Kitaev interactions is parametrized by a coupling angle $\varphi$, defined by $J=cos\varphi$ and $K=sin\varphi$. By combining energy-based diagnostics with finite-size extrapolations of order parameters and correlation functions, we obtain a comprehensive phase diagram as a function of $\varphi$ and $D_z$. The phase diagram contains ferromagnetic and Néel ordered phases, collinear states with four-site spin modulation, magnetically disordered or critical regimes, two Kitaev-dominated spin-liquid-like regions, and a topological Haldane phase near the Heisenberg limit. We find that the Kitaev-dominated disordered regions acquire finite parameter widths in the spin-1 model, whereas the Haldane phase is fragile against Kitaev-type anisotropy, especially for $D_z<0$. Positive $D_z$ generally suppresses magnetic order and expands nonmagnetic regimes, while negative $D_z$ enhances Ising-like magnetic order. At $D_z=0$, we also identify an exactly solvable point at $tan\varphi =-2(\varphi /\pi \simeq 1.6476)$, which gives rise to a first-order transition between the Néel-$z$ state and a four-site collinear state. We further contrast these findings with the spin-$1/2$ KH chain and with the spin-1 honeycomb KH model, highlighting the distinct roles of single-ion anisotropy and dimensionality in Kitaev-type magnets.

We demonstrate precise control of exchange bias (EB) in the ${\mathrm{Nd}}_{2-x}{\mathrm{Sr}}_x{\mathrm{CoMnO}}_{6-\delta }$ $(0\le x\le 1)$ double-perovskite series through ${\mathrm{Sr}}^{2+}$-induced hole doping, revealing a remarkable transition between normal and inverse EB. Using neutron powder diffraction and x-ray absorption spectroscopy, we uncover a structural evolution from a $B$-site-ordered monoclinic $(P{2}_1/n)$ to a disordered rhombohedral $\left(R\overline{3}c\right)$ phase with increasing $x$. This transition is accompanied by a shift in the effective Co valence from $+2$ toward $+3$, while the Mn valence remains close to $+3.6$ throughout the series. DC magnetization measurements indicate a gradual suppression of ferromagnetism with hole doping, whereas ac magnetization measurements for $x=0.75$ reveal pronounced cluster-glass behavior. Notably, $x=0.75$ also exhibits the highest EB field of $\sim 4$ kOe at 8 K under a 20 kOe cooling field. After correcting for minor-loop effects, we identify robust inverse EB at $x=0.75$, persisting even under a 60 kOe cooling field. The coexistence of pronounced glassiness with large EB fields and robust inverse EB suggests that interfacial interactions involving frustrated spins play a central role in stabilizing these exotic EB states. Furthermore, the apparent nonmonotonic evolution of the measured EB with doping is found to be largely influenced by minor-loop effects. After correcting for these effects, the intrinsic EB exhibits an overall reduction with increasing doping and antisite disorder. Interestingly, the intrinsic EB displays a local maximum when the ferromagnetic and nonferromagnetic phase fractions become comparable, despite the persistence of strong glassy dynamics across the series. These findings establish rare-earth double perovskites as a promising platform for engineering tunable EB functionalities through controlled structural disorder and magnetic phase competition, opening new avenues for advanced spintronic and magnetic memory applications.

Indium selenide (${\mathrm{In}}_2{\mathrm{Se}}_3$) exhibits significant phase transition behavior and relatively weak interlayer interactions, resulting in greater compressibility under pressure compared to other transition metal dichalcogenides. Hydrostatic pressures up to 11.9 GPa were applied to probe the structural evolution and stability of $\alpha /\beta \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$ van der Waals heterojunctions. The shift of the $A_1^3$ mode to the $E_g^2$ mode near 2 GPa marks the transformation of $\alpha \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$ into ${\beta }^{\prime }\text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$. The disappearance of the $E^2, A_1^2$, and $E^4$ modes around 6 GPa signals the subsequent transition to $\beta \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$. The Raman intensity mapping of the $A_1^1 \to A_g^4 \to E_g^2$ mode under pressure further delineates the complete phase transition pathway, confirming that the heterojunction remains stable between 0 and 2 GPa and converts entirely to $\beta \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$ beyond 6 GPa. Finally, an intrinsic correlation mechanism among pressure, structural distortion, electronic band structure, and thermodynamic stability is established via first-principles calculations. These findings advance the understanding of stress-mediated structural evolution in $\alpha /\beta \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$ heterojunctions and support the design of strain-engineered devices.

The kagome metal ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ hosts an anomalous interplay between charge density wave (CDW) order and superconductivity—one where tuning its band filling by adding holes rapidly suppresses long-range CDW order and drives the formation of two unusual superconducting “domes.” Here, we determine the detailed evolution of charge correlations across the two domes of hole-doped ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ and resolve their interplay with the superconducting state. Upon light hole doping, the suppression of a metastable CDW state coincides with quenching superconducting fluctuations present in the parent ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ compound. Continued doping suppresses long-range CDW order, leaving remnant short-range correlations that persist across the second superconducting dome. These remnant correlations present in a quasi-one-dimensional correlation volume with a central wave vector approaching a single-$\mathbf{q}R$-point instability, whose stabilization is captured in ab initio models. The microscopic nature of the competing single-$\mathbf{q}$ CDW is resolved as short-range V-V dimers, which break rotational and translational symmetry locally throughout the second superconducting dome and whose presence coincides with a superconducting ground state.

The metal-superconductor point contact (PC) is ballistic, if the coherence length ${\xi }_0$ in the superconductor, the electron mean free path $l_0$ in the metal, and the electron mean free path $l$ in the superconductor are much larger than the PC radius $a$. The differential conductance $G\left(V\right)$ of the ballistic PC at low temperatures and at voltages $\left|V\right|\le \mathrm{\Delta }/e$, where $\mathrm{\Delta }$ is the superconducting gap, exhibits the Andreev peak caused by Andreev reflection. In the ballistic PC involving an isotropic superconductor, the Andreev peak at $\left|V\right|\le \mathrm{\Delta }/e$ normalized by the background conductance $G\left(V\right)$ at $\left|V\right|\gg \mathrm{\Delta }/e$, is equal to two. It is believed that in a disordered PC, where conditions $l_0,l\gg a$ fail, the normalized Andreev peak is smaller than two. Here we study the PC between a clean metal ($l_0\gg a$) and a weakly disordered ($l\gtrsim a$) isotropic superconductor in the limit $l\ll {\xi }_0$. We show theoretically and experimentally that, surprisingly, disorder on the superconducting side, however weak, raises the normalized Andreev peak above the ballistic value of two. Such disorder does not affect the Andreev reflection and $G\left(V\right)$ at $\left|V\right|<\mathrm{\Delta }/e$. However, it scatters the quasiparticles injected into the superconductor above the gap and reflects a part of them back to the PC before they join the condensate. As a result, $G\left(V\right)$ at $\left|V\right|>\mathrm{\Delta }/e$ is lowered and the Andreev peak-to-background ratio becomes larger than two. In the normal state, the backscattering modifies the Sharvin-Maxwell PC resistance by adding a coherent resistance term $\propto {(a/l)}^2$.

It has been suggested that noninvertible symmetry-protected topological phases (SPT), due to the lack of a stacking structure, do not have symmetric entanglers (globally symmetric finite-depth quantum circuits) connecting them. Using topological holography, we argue that a symmetric entangler should in fact exist for $1+1\mathrm{D}$ systems whenever the noninvertible symmetry has SPT phases connected by fixed-charge dualities. Moreover, we construct an explicit example of a symmetric entangler for the two SPT phases with $\mathrm{Rep}\left(A_4\right)$ symmetry, as a matrix product unitary.

Motivated by recent angle-resolved photoemission spectroscopy (ARPES) experiments on infinite-layer (IL) nickelates, we employ determinant quantum Monte Carlo (DQMC) to study the three-orbital Emery model ($d\text{−}p$ model) coupled to an additional interstitial $s$ orbital that retains the three-dimensional dispersion. Our large-scale simulations reveal that: (1) the interstitial $s$-orbital-derived electron pocket is significantly reduced by strong interactions but persists upon 20% hole doping, reaching a size comparable to experimental observations; (2) the $d_{x^2-y^2}$-orbital dispersion is strongly renormalized by interactions, leading to a weak $k_z$ dependence consistent with ARPES measurements. Furthermore, compared with the conventional three-orbital $d\text{−}p$ model, the $d\text{−}p\text{−}s$ model exhibits enhanced short-range antiferromagnetic correlations. These results highlight the crucial role of strong correlations and multiorbital effects in shaping the low-energy electronic structure and many-body correlations in IL nickelates and demonstrate the necessity of treating interaction-driven many-body physics within a realistic multiorbital framework.