We investigate the fundamental dynamical process of an initial quench of the chemical potential of the two-dimensional $t\text{−}J$ model. Depending on the ground-state phase, sharply different dynamical behaviors of the charge distribution and entanglement properties are observed. In the stripe phase, the intertwining of the spin and charge density waves remains stable under time evolution. A ballistic spreading of the charge density is observed with a propagation speed that is only weakly dependent on the coupling ratio $J/t$. Moreover, in the phase-separated regime for large $J/t$, we report a complete dynamical freezing of charge degrees of freedom within, where even under long time evolution the entanglement entropy remains bounded. Our results are obtained by combining large-scale exact-diagonalization and matrix-product-state techniques for time evolution.

Recent experimental study on ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+x}$ superconductors has revealed an unexpected quantum phase transition from superconducting state to insulatinglike state under pressure [Zhou et al., Nat. Phys. 18, 406 (2022)]. To better understand the physical origin of this pressure-induced phenomenon, here we have studied the structural, electronic, and magnetic properties of undoped and O-doped ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+x}$ (Bi2212) under pressures based on density-functional theory calculations. We first identified the crystal structure of undoped Bi2212 with the armchair distortions in the BiO layers and reproduced the insulating feature of the parent compound. Then we added an extra O atom to the parent compound to simulate the hole-doping effect and found that the structure with O dopant located in the van der Waals (vdW) gap is energetically the most stable. Further calculations on O-doped (0.125 holes/Cu) Bi2212 revealed that the pressure can induce charge redistributions between ${\mathrm{CuO}}_2$ planes and BiO layers; specifically, Cu-$d_{x^2-y^2}$ orbitals gain electrons and Cu atoms rather than O atoms dominate around the Fermi level under high pressure. Along with the increasing pressure, the density of states at the Fermi level first reaches the maximum at $\sim 10$ GPa and then shows a valley near the Fermi level above 20 GPa, which may be responsible for the insulatinglike state observed in recent experiments. We suggest that the competition among several factors, such as the increase of electrons in the ${\mathrm{CuO}}_2$ plane, the variation of in-plane hopping due to the shortened Cu-O distance, and the enhanced Coulomb repulsion among the $\mathrm{Cu-3}d$ electrons, could lead to the exotic transition under pressure. Our work provides an explanation of the high-pressure behaviors of Bi2212, which may facilitate a comprehensive understanding of cuprate superconductors.

Localized surface plasmons (LSPs) are collective oscillations of free electrons in metal nanoparticles that confine electromagnetic waves into subwavelength regions, making them an ideal platform for light-matter coupling. To design and understand plasmonic structures, numerical computations of Maxwell's equations are commonly used. However, obtaining physical insight from these numerical solutions can be challenging, especially for complex-shaped nanoparticles. To circumvent this, we introduce mode decomposition strategies within the boundary element method. By employing singular value decomposition (SVD) and quasinormal-mode (QNM) decomposition, we break down optical responses into elementary modes. QNMs offer deeper insights into frequency and damping, while SVD modes allow for more accurate spectral reconstruction with fast computation. These techniques provide a deeper understanding of LSPs and facilitate the design of metal nanoparticles for efficient light-matter interaction.

We argue that moiré bilayer graphene at charge neutrality hosts a continuous semimetal-to-insulator quantum phase transition that can be accessed experimentally by tuning the twist angle between the two layers. For small twist angles near the first magic angle, the system realizes a Kramers intervalley-coherent insulator, characterized by circulating currents and spontaneously broken time reversal and U(1) valley symmetries. For larger twist angles above a critical value, the spectrum remains gapless down to the lowest temperatures, with a fully symmetric Dirac semimetal ground state. Using self-consistent Hartree-Fock theory applied to a realistic model of twisted bilayer graphene, based on the Bistritzer-MacDonald Hamiltonian augmented by screened Coulomb interactions, we find that the twist-tuned quantum phase transition is continuous. We argue that the quantum critical behavior belongs to the relativistic Gross-Neveu-XY universality class, and we characterize it through an effective field theory analysis. Our theoretical predictions can be directly tested using current experimental setups incorporating the recently developed quantum twisting microscope.

Nitrogen, known for its rich polymorphism and kinetic barriers, has served as a valuable testbed for evaluating advanced computational methods. In this study, we investigate the infrared absorptions of $\gamma \text{−}{\mathrm{N}}_2$, a crystalline molecular configuration that is only accessible via a low-temperature compression, employing synchrotron radiation. Our results reveal that $\gamma \text{−}{\mathrm{N}}_2$ possesses a simple infrared spectrum consisting of only three far-infrared phononic absorptions: a prominent asymmetric peak made up of two unresolved modes, and a weak higher-frequency peak, all of which could be tracked up to 93 GPa. Critically, no absorption associated with an internal vibrational mode of the ${\mathrm{N}}_2$ molecule was detected up to the highest pressures. Density functional theory (DFT) simulations conducted at 40 GPa demonstrate that these observations align with the $P{2}_1/c$ structural model, reinforcing its compatibility as a candidate complimenting existing Raman and x-ray diffraction results. Finally, our findings, in conjunction with measurements made over 50 years ago, further support that the formerly assigned “anomalous”/$\lambda {\mathrm{N}}_2$-phase is in fact the long-established $\gamma \text{−}{\mathrm{N}}_2$ phase.

We report $\beta$-detected nuclear magnetic resonance $\left(\beta \mathrm{NMR}\right)$ measurements of implanted ${}^8\mathrm{Li}^{+}$ in a synthetic single crystal of $\alpha \text{−}{\mathrm{SiO}}_2$ (quartz). At 6.55 Tesla, the spectrum is comprised of a large amplitude broad resonance and a quadrupolar multiplet that is only revealed by an rf comb excitation. The quadrupole splitting is surprisingly small, increases with temperature, and provides information on the implantation site. Supercell density functional theory calculations show the splitting is consistent with an in-channel interstitial site (Wyckoff $3a$). The spin-lattice relaxation is unexpectedly fast and strongly temperature dependent with a diffusive peak above 200 K and a second more prominent relaxation peak at lower temperature. Analysis of the diffusive relaxation yields an activation barrier 178(43) meV for the isolated ${\mathrm{Li}}^{+}$ in the range of other measurements and calculations. To account for many of the other features of the data, it is suggested that some of the implanted ions trap an electron forming the neutral ${\mathrm{Li}}^0$, which is stable over a narrow range of temperatures.

The vibrational modes in ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$ easily induce octahedral rotations without tilting. Being on the verge of a magnetic instability, such propensity of octahedral rotation may also produce magnetic fluctuations. In this work, we analyze the long-range magnetic phase diagram incorporating such octahedral rotations and demonstrate the possibility of an altermagnetic phase in ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$. Using ab initio calculations, we first study single-layer ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$ with octahedral rotations, obtaining an orbital-selective $g$-wave altermagnetic phase. We further provide an effective $t_{2g}$ tight-binding model, demonstrating that the $g$-wave altermagnetism is primarily a product of second- and third-nearest-neighbor interorbital hybridizations between the $\gamma z$ ($\gamma =x,y$) orbitals, but only a much longer range intraorbital hybridization in the $xy$ orbitals, establishing a strong orbital selectiveness for the altermagnetism. Notably, by replacing the $xy$ orbital with the $x^2-y^2$ orbital, a similar tight-binding model may be used to investigate the hole-doped cuprate superconductors. We then study bulk ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$, where we find the altermagnetic phase as the magnetic ground state for a range of finite octahedral rotations. In the bulk, interlayer hopping breaks some of the symmetries of the $g$-wave altermagnet, resulting in a $d_{xy}$-wave altermagnet, still with orbital selectiveness. We also include relativistic effects through spin-orbit coupling and obtain that an effective staggered Dzyaloshinskii-Moriya interaction generates weak ferromagnetism. Finally, we discuss the implications of the altermagnetic order on the intrinsic superconductivity of ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$. Assuming in-plane intraorbital pairing, the altermagnetism favors spin-singlet $d_{x^2-y^2}$-wave or $g$-wave pairing, or their combinations.

The dynamics of magnetic moments coupled to phonons is of great interest for understanding spin transport in solids as well as for our ability to control magnetism via tailored phonon modes. For spin $S>\frac{1}{2}$, spin-orbit coupling permits an unusual linear coupling of phonons to quadrupolar moments, so that phonons act as a dynamical transverse field for the spins. Here, we develop a generalized $\text{SU}\left(N\right)$ spin-phonon Monte Carlo and molecular dynamics technique to simulate the equilibrium and nonequilibrium properties of such spin-orbital-phonon coupled Mott insulators, and apply it to a spin-1 model with competing XY antiferromagnet (AFM) and quadrupolar paramagnet (QPM) phases. We uncover a rich set of nonequilibrium phenomena from driven phonons, including the generation of a uniform magnetization in the QPM and AFM, strengthening of Néel order, gapping of the AFM Nambu-Goldstone mode by Floquet-Ising anisotropy, and creating Floquet copies of transverse and longitudinal spin waves. Our work is relevant for driven spin-1 magnets, such as ${\mathrm{Ba}}_2{\mathrm{FeSi}}_2{\mathrm{O}}_7$, and we highlight broader implications for nonequilibrium multipolar magnetism.

Recent experiments have shown that the edge states of a quantum Hall sample can be coupled to a superconductor, so that incoming electrons can be Andreev converted by the superconductor as coherent superpositions of an electron and a hole. In parallel, single-electron emitters that operate in the gigahertz regime have been realized in circuits based on quantum Hall edge states. Motivated by this remarkable experimental progress, we analyze here the Andreev reflections of incoming charge pulses on the interface with a superconductor. To this end, we employ a Wigner function representation that allows us to visualize the response function of the interface in both the time and frequency domains. We analyze the response of an interface between a normal metal and a singlet or triplet superconductor with and without an insulating barrier between them. As a special case, we analyze the Andreev reflections of clean single-particle excitations that are generated by the application of Lorentzian-shaped voltage pulses to the contacts of the inputs. Our predictions may be tested in future experiments with edge states coupled to superconductors.

The transition metal dichalcogenide $4H_b\text{−}{\mathrm{TaS}}_2$ exhibits characteristics of topological edge modes and two-component superconductivity with time-reversal symmetry breaking (TRSB). The nature of the superconducting order parameter is a crucial issue that requires experimental investigation. Here, we report measurements of the magnetic penetration depth using a tunnel-diode-oscillator based technique, as well as the specific heat. Both the specific heat and the change in magnetic penetration depth $\left[\mathrm{\Delta }\lambda \left(T\right)\right]$ display an exponentially activated temperature dependence, providing evidence for nodeless superconductivity in $4H_b\text{−}{\mathrm{TaS}}_2$. Moreover, the deduced superfluid density can be well described by a two-gap $s$-wave model, and such multigap superconductivity is consistent with there being multiple bands crossing the Fermi energy. These results constrain the possible pairing symmetries of $4H_b\text{−}{\mathrm{TaS}}_2$.

Two approaches to the calculation of phase diagrams for materials under high pressures and temperatures with the use of ab initio molecular dynamics are discussed. The first is based on calculations of vibrational free energies of crystal phases with the temperature-dependent effective potential, and the second is based on calculations of thermodynamic potentials with the thermodynamic integration technique combined with machine learning accelerated quantum molecular dynamics with moment tensor potential. Detailed consideration is given to methodical issues. The emphasis of the paper is on phase diagram calculation for uranium in the region where its three solid phases (orthorhombic $\alpha$, body-centered-cubic $\gamma$, and body-centered-tetragonal ${\gamma }^{\prime }$) exist ($P<400\text{GPa}$ and $T<6000\text{K}$). It is shown that the position of equilibrium lines on the phase diagram is sensitive to the choice of theoretical approximation [density functional theory (DFT), $\mathrm{DFT}+U$], but phase diagram topology (the phases and their relative positions) on the $P\text{−}T$ plane is not if the accuracy of thermodynamic potential calculations is below 3–$5\text{meV/at}$. Comparison with calculations by other authors and with available experimental data is provided. The prediction of a triple point $\alpha \text{−}\gamma \text{−}{\gamma }^{\prime }$ at $P\sim 100\text{GPa}$ and $T\sim 2400\text{K}$ in the calculation may be of interest in view of its possible verification in experiments in laser-heated diamond anvil cells.

It is well known that unitary evolution tends to increase entanglement, whereas continuous monitoring counteracts this growth by pinning the wave-function trajectories to the eigenstates of the measurement operators. In this work, we investigate the fate of the measurement-induced phase transition in a periodically driven free-fermionic quantum system, where the hopping amplitude is modulated periodically in time using a square pulse. In the high-frequency limit, a renormalization group analysis of the non-Hermitian quantum sine-Gordon model [as proposed in Phys. Rev. X 11, 041004 (2021)] reveals that if the hopping amplitude is varied symmetrically around zero, then the system always favors the area-law phase, where the steady-state entanglement entropy is independent of subsystem size. In contrast, asymmetry in the drive amplitudes tends to promote entanglement growth. Furthermore, numerical evidence for the system sizes accessible to us suggests that decreasing the drive frequency typically favors entanglement growth. For such driven systems, at least for reasonably small frequency regimes, as a function of measurement strength, we observe a potential signature of a Berezinskii-Kosterlitz-Thouless phase transition between a gapless critical phase, characterized by logarithmic growth of entanglement entropy with subsystem size and a gapped area-law phase. However, it is almost impossible to rule out the possibility that the transition observed here is not an actual thermodynamic transition but a finite-size crossover between logarithmic to area-law entanglement phase. Even in that scenario, the critical length scale beyond which the area-law phase prevails increases with the increasing time period of driving. On the other hand, for a symmetric drive, the system consistently exhibits an area-law phase, regardless of the driving frequency.

We develop a systematic large-$N$ expansion based on the Schwinger boson representation of SU(4) coherent states of dimers for the paradigmatic spin-$1/2$ bilayer square lattice Heisenberg antiferromagnet. This system exhibits a quantum phase transition between a quantum paramagnetic state and a Néel order state, driven by the coupling constant $g=J^{\prime }/J$, which is defined as the ratio between the interdimer $J^{\prime }$ and intradimer $J$ exchange interactions. We demonstrate that this approach accurately describes static and dynamic properties on both sides of the quantum phase transition. The critical coupling constant $g_c\approx 0.42$ and the dynamic spin structure factor reproduce quantum Monte Carlo results with high precision. Notably, the $1/N$ corrections reveal the longitudinal mode of the magnetically ordered phase along with the overdamping caused by its decay into the two-magnon continuum. The present large-$N$ SU(4) Schwinger boson theory can be extended to more general cases of quantum paramagnets that undergo a quantum phase transition into magnetically ordered states.

We present a comprehensive spectroscopic mapping of phonon, magnetic, electron-hole, and spin-orbit (SO) excitonic excitations across the insulator-to-metal transition (IMT) in the solid solution $\mathrm{Ru}{\left({\mathrm{Br}}_{1-x}{\mathrm{I}}_x\right)}_3$ using Raman spectroscopy. This material series offers a unique platform to explore SO-entangled magnetism, bridging the SO-assisted Mott insulator ${\mathrm{RuBr}}_3$ and the correlated semimetal ${\mathrm{RuI}}_3$. With increasing iodine content, we observe a systematic softening of phonon modes, suppression of the zigzag antiferromagnetic order, and a gradual dominance of electron-hole excitations over SO excitons. For $x\ge 0.6$, two-magnon Raman scattering is suppressed, while an electron-hole continuum emerges above $x\approx 0.85$, coinciding with the IMT threshold. Remarkably, ${\mathrm{RuI}}_3$ displays a weakly increasing $\omega$ dependence of its Raman response and power-law growth of the dynamic Raman susceptibility, indicative of a spin-liquid-like behavior. Theoretical modeling corroborates the persistence of $j_{\text{eff}}=\frac{1}{2}$ moments on the metallic side, despite partial electronic delocalization. Our results provide insights into the interplay between SO coupling, electronic correlations, and structural distortions in collectively driving the IMT in SO-entangled systems.

Chiral magnetic textures are key for the development of modern spintronic devices. In multilayered thin films, these are typically stabilized via the interfacial intralayer Dzyaloshinskii-Moriya interaction (DMI). Additionally, it has been recently observed that DMI may also promote vector spin chirality along the third dimension, coupling spins in different magnetic layers via nonmagnetic spacer layers, an effect referred to as interlayer DMI (IL-DMI). This interaction holds promise for 3D nanomagnetism, from the creation of 3D spin structures such as hopfions to new forms of magnetic functionality in the vertical direction via remote control of chiral spin states. In this work, we provide direct experimental evidence that the in-plane vector spin chirality of magnetic textures within a ferromagnetic layer can be controlled via the net out-of-plane spin configuration of an adjacent one. Both ferromagnetic layers form part of a synthetic antiferromagnet, previously shown to have IL-DMI. This in-plane vector chirality dependence on the out-of-plane configuration of another layer implies that the overall scalar spin chirality is preserved when computed across layers. We draw these conclusions from a combination of magnetic x-ray scattering and imaging experiments, complemented by various simulations. These findings thus uncover a type of chiral interlayer interactions, which can lead to the formation of intricate spin states across a metallic interface, demonstrating other ways to control magnetic chirality in three dimensions.

Evidence for developing fractional quantum Hall effect (FQHE) at filling fraction $\nu =1/6$ and $1/8$ was recently reported in wide GaAs quantum wells [Wang et al., Phys. Rev. Lett. 134, 046502 (2025)]. In this article, we theoretically investigate the nature of the state at $\nu =1/6$ as a function of the quantum well width and the density by considering composite-fermion (CF) crystals, CF Fermi sea, and various kinds of paired CF states. The $f$-wave paired state has the lowest energy among the paired CF states. However, for parameters of interest, the energies of the CF crystal, the CF Fermi liquid, and the $f$-wave paired CF state are too close to distinguish. We, therefore, predict that $\mathit{if}$ the FQHE at $\nu =1/6$ is experimentally confirmed, this state would be an $f$-wave paired state of CFs, which can be verified by measurement of its thermal Hall conductance. Exact diagonalization studies on clean systems with up to eight electrons show that the ground states at $\nu =n/(6n\pm 1)$ are incompressible for all widths and densities we have considered, and are well described by the corresponding Laughlin and Jain states. We propose a phase diagram for large quantum well widths and densities in which at zero disorder, incompressible FQHE states are stabilized at $\nu =n/(6n\pm 1)$ and $\nu =1/6$, but in between these fillings the CF crystal is stabilized. We also present a qualitative discussion on the effects of disorder and propose a schematic phase diagram based on it. With disorder, which creates a spatial variation in the filling factor, two regimes are identified: (i) for small disorder, when the incompressible states percolate at the special fillings, FQHE with quantized Hall plateaus and vanishing longitudinal resistance should occur; and (ii) for larger disorder, when the CF crystal percolates, the longitudinal resistance rises with decreasing temperature but the domains of FQHE liquid produce minima at the special filling factors. Experiments are consistent with the latter scenario. We also mention a possible connection of the phase diagram presented here to a puzzling behavior observed for the fractional quantum anomalous Hall effect in pentalayer graphene.

A method of using partial symmetries to distinguish two-dimensional symmetry protected topological (SPT) phases of on-site, unitary symmetries is proposed. This novel order parameter takes a wave function, such as a ground state of a lattice model, and detects its SPT invariants as expectation values of finitely supported operators, without the need for flux insertion. The construction exploits the rotational symmetry of the lattice to extract on-site SPT invariants, building upon prior work on probing crystalline SPT phases with partial rotations. The method is demonstrated by computing the order parameter analytically on group cohomology models and numerically on a family of states interpolating between the CZX state and a trivial state. Its robustness is suggested by interpreting partial symmetries as generating the topological partition functions of lens spaces.

Local relevant deformations are an important tool to study universal properties of quantum critical points. We investigate the effect of small relevant deformations on the bipartite entanglement entropy at the quantum critical points. Within the quantum critical region, a universal power-law correction in the entanglement entropy induced by the relevant operator is found in both one- and two-dimensional critical lattice models. The exponent of the power-law correction term is determined by the scaling dimension of the relevant operator. Based on numerical simulations and scaling theory argument, it is conjectured that such a universal power-law correction in the entanglement entropy is universal for Lorentz invariant quantum critical points. Without Lorentz invariance, it is found the exponent in the power-law correction term does not fit in with the scaling argument in models with a dynamical exponent $z=2$ in two dimensions. This may be because the relevant operator added in the lattice model corresponds to complicated operators in the corresponding conformal field theory. Our study provides a different perspective to extract universal information of quantum critical points. We expect it would be useful to detect unique properties of topological quantum phase transitions.

Strange metals exhibit linear resistivity and anomalous Hall transport, yet a comprehensive theory that accounts for both phenomena is still lacking. Recent studies have shown Sachdev-Ye-Kitaev-like spatially random couplings between a Fermi surface and a bosonic field, either scalar or vector type, can yield linear-$T$ resistivity. In this paper, we continue the investigation of vector coupling in the presence of a magnetic field. We compute the fermion and boson propagators, along with the self-energy and polarization functions, and determine their dependence on the magnetic field. Although the Hall angle does not exhibit the signature of a strange metal, the linear-in-temperature resistivity remains at low temperatures. Results indicate that random interactions can robustly support linear transport, although additional ingredients may be required to capture the full phenomenology of strange metals.