Materials typically fail under complex stress states, essentially involving dilatational (volumetric) components that eventually lead to material decohesion/separation. It is therefore important to understand dilatational irreversible deformation—i.e., dilatational plasticity—en route to failure. In the context of glasses, much focus has been given to shear (volume-preserving) plasticity, both in terms of the stress states considered and the corresponding material response. Here, using a recently developed methodology and extensive computer simulations, we shed basic light on the elementary processes mediating dilatational plasticity in glasses. We show that plastic instabilities, corresponding to singularities of the glass Hessian, generically feature both dilatational and shear irreversible strain components. The relative magnitude and statistics of the strain components depend both on the symmetry of the driving stress (e.g., shear versus hydrostatic tension) and on the cohesive (attractive) part of the interatomic interaction. We further show that the tensorial shear component of the plastic strain is generally nonplanar and also extract the characteristic volume of plastic instabilities. Elucidating the fundamental properties of the elementary micromechanical building blocks of plasticity in glasses sets the stage for addressing larger-scale, collective phenomena in dilatational plasticity such as topological changes in the form of cavitation and ductile-to-brittle transitions. As a first step in this direction, we show that the elastic moduli markedly soften during dilatational plastic deformation approaching cavitation.

Spurred by the recent development of fracton topological phases, unusual topological phases possessing fractionalized quasiparticles with mobility constraints, the concept of symmetries has been renewed. In particular, in accordance with the progress of multipole symmetries, associated with conservation of multipoles, such as dipole or quadruple moments as well as global charges, there have been proposed topological phases with such symmetries. These topological phases are unconventional because excitations are subject to mobility constraints corresponding to the multipole symmetries. We demonstrate a way to construct such phases by preparing layers of symmetry protected topological (SPT) phases and implementing gauging a global symmetry. After gauging, the statistics of a fractional excitation is altered when crossing the SPT phases, resulting in topological phases with the multipole symmetries. The way we construct the phases allows us to have a comprehensive understanding of field theories of topological phases with the multipole symmetries and other fracton models.

The superconducting (SC) cuprate ${\mathrm{HgBa}}_2{\mathrm{Ca}}_2{\mathrm{Cu}}_3{\mathrm{O}}_8$ (Hg1223) has the highest SC transition temperature $T_c$ among cuprates at ambient pressure $P_{\mathrm{amb}}$, namely, $T_c^{\mathrm{opt}}\simeq 138$ K experimentally at the optimal hole doping concentration. $T_c^{\mathrm{opt}}$ further increases under pressure $P$ and reaches 164 K at optimal pressure $P_{\mathrm{opt}}\simeq 30$ GPa, then $T_c^{\mathrm{opt}}$ decreases with increasing $P>P_{\mathrm{opt}}$ generating a dome structure [Gao et al., Phys. Rev. B 50, 4260(R) (1994)]. This nontrivial and nonmonotonic $P$ dependence of $T_c^{\mathrm{opt}}$ calls for a theoretical understanding and mechanism. To answer this open question, we consider the ab initio low-energy effective Hamiltonian (LEH) for the antibonding (AB) $\mathrm{Cu}3d_{x^2-y^2}/\mathrm{O}2p_{\sigma }$ band derived generally for the cuprates. In the AB LEH for cuprates with $N_{\ell }\le 2$ laminated ${\mathrm{CuO}}_2$ planes between block layers, it was proposed that $T_c^{\mathrm{opt}}$ is determined by a universal scaling $T_c^{\mathrm{opt}}\simeq 0.16\left|t_1\right|F_{\mathrm{SC}}$ [Schmid et al., Phys. Rev. X 13, 041036 (2023)], where $t_1$ is the nearest-neighbor hopping, and the SC order parameter at optimal hole doping $F_{\mathrm{SC}}$ mainly depends on the ratio $u=U/|t_1|$ where $U$ is the onsite effective Coulomb repulsion: The $u$ dependence of $F_{\mathrm{SC}}$ has a peak at $u_{\mathrm{opt}}\simeq 8.5$ and a steep decrease with decreasing $u$ in the region $u<u_{\mathrm{opt}}$ irrespective of materials dependent on other ab initio parameters. In this paper, we show that $|t_1|$ increases with $P$, whereas $u$ decreases with $P$ in the ab initio Hamiltonian of Hg1223. Based on these facts, we show that the domelike $P$ dependence of $T_c^{\mathrm{opt}}$ can emerge at least qualitatively if we assume Hg1223 with $N_{\ell }=3$ follows the same universal scaling for $T_c^{\mathrm{opt}}$, and Hg1223 is located at the slightly strong coupling region $u\gtrsim u_{\mathrm{opt}}$ at $P_{\mathrm{amb}}$ and $u\simeq u_{\mathrm{opt}}$ at $P_{\mathrm{opt}}$ by taking account of expected corrections to our ab initio calculation. The consequence of these assumptions is the following: With increasing $P$ within the range $P<P_{\mathrm{opt}}$, the increase in $T_c^{\mathrm{opt}}$ is accounted for by the increase in $|t_1|$, whereas $F_{\mathrm{SC}}$ is insensitive to the decrease in $u$ around $\simeq u_{\mathrm{opt}}$ and hence to $P$ as well. At $P>P_{\mathrm{opt}}$, the decrease in $T_c^{\mathrm{opt}}$ is accounted for by the decrease in $u$ below $u_{\mathrm{opt}}$, which causes a rapid decrease in $F_{\mathrm{SC}}$ dominating over the increase in $|t_1|$. We further argue the appropriateness of these assumptions based on the insight from studies on other cuprate compounds in the literature. In addition, we discuss the dependencies of $u$ and $|t_1|$ on each crystal parameter (CP), which provides hints for design of even higher $T_c^{\mathrm{opt}}$ materials.

We study the effects of the interplay of weak disorder and weak coupling in a system of parametric micromechanical oscillators. Each oscillator is bistable, enabling the mapping of its stable states onto spin states. The coupling changes the rate of interstate switching of an oscillator depending on the state of other oscillators. We demonstrate that the change is exponentially strong and therefore manifests even for weak coupling. Difference in the oscillator eigenfrequencies translates into disorder in the system. The analysis and the experiment show that disorder leads to a nontrivial stationary state that displays current. The system provides a well-controlled and fully characterized implementation of the asymmetric Ising model, in which coupled spins affect each other differently. This model plays an important role in physics and biology. Our findings open the possibilities of constructing and exploring asymmetric Ising systems with controlled parameters and connectivity.

Nonlinear optical signals in optically driven quantum systems can reveal coherences and thereby open up the possibility for manipulation of quantum states. While the limiting cases of ultrafast and continuous-wave excitation have been extensively studied, the time dynamics of finite pulses bear interesting phenomena. In this paper, we explore the nonlinear optical probe signals of a two-level system excited with a laser pulse of finite duration. In addition to the prominent Mollow peaks, the probe spectra feature several smaller peaks for certain time delays. Similar features have been recently observed for resonance fluorescence signals [K. Boos et al., Phys. Rev. Lett. 132, 053602 (2024)]. We discuss that the emergent phenomena can be explained by a combination of Mollow triplet physics and perturbed free induction decay effects, providing an insightful understanding of the underlying physics.

High mobility two-dimensional systems with superposed 1D lateral periodic potentials exhibit characteristic commensurability (Weiss) oscillations that reflect the interplay of the cyclotron radius at the Fermi level and the superlattice period. Here, we impose a one-dimensional periodic potential on strained HgTe, which is a strong 3D topological insulator. By tuning the Fermi level with top gates, the effects of the artificial potential can be studied in the bulk gap, where only Dirac surface states exist, in the conduction band, and in the valence band, where Dirac electrons and holes coexist. On the electron side, we observe clear commensurability oscillations whose period is governed by the carrier density of the top-surface Dirac electrons. Unexpectedly, weak commensurability oscillations are also observed in the valence band with a period that depends on both electron and hole density.

We predict a scheme for the creation of isotropic three-dimensional quantum droplets in Rydbeg-dressed Bose gases, which contain both repulsive contact interactions and attractive soft-core interactions. Via manipulating laser detuning, the droplet size and particle number density could be engineered. Quantum fluctuation induced Lee-Huang-Yang (LHY) correction should be considered to stabilize droplets when LHY energy is comparable to the mean-field energy. Self-trapped droplets possess flat-top density distribution for a large particle number, and the collective excitations are calculated to determine the self-evaporation threshold. We further distinguish quantum droplets from solitons according to condensate compressibility. Finally, the dynamic stability of droplets is examined by pairwise-droplet collision. Our system could realize the most dilute quantum droplets, and establish a promising platform for further simulating topological nontrivial droplets.

We introduce a variational manifold of simple tensor network states for the study of a family of constrained models that describe spin-$\frac{1}{2}$ systems as realized by Rydberg atom arrays. Our manifold permits analytical calculation via perturbative expansion of one- and two-point functions in arbitrary spatial dimensions and allows for efficient computation of the matrix elements required for variational energy minimization and variational time evolution in up to three dimensions. We apply this framework to the PXP model on the hypercubic lattice in one, two, and three dimensions and show that, in each case, it exhibits quantum phase transitions breaking the sublattice symmetry in equilibrium, and hosts quantum many-body scars out of equilibrium. We demonstrate that our variational ansatz qualitatively captures all these phenomena and predicts key quantities with an accuracy that increases with the dimensionality of the lattice, and conclude that our method can be interpreted as a generalization of mean-field theory to constrained spin models.

We investigate self-localization of a polaron in a homogeneous Bose-Einstein condensate in one dimension. This effect, where an impurity is trapped by the deformation that it causes in the surrounding Bose gas, has been first predicted by mean-field calculations, but has not been seen in experiments. We study the system in one dimension, where, according to the mean-field approximation, the self-localization effect is particularly robust and present for arbitrarily weak impurity-boson interactions. We address the question whether self-localization is a real effect by developing a variational method which incorporates impurity-boson correlations nonperturbatively and solving the resulting inhomogeneous correlated polaron equations. We find that correlations inhibit self-localization except for very strongly repulsive or attractive impurity-boson interactions. Our prediction for the critical interaction strength for self-localization agrees with a sharp drop of the inverse effective mass found in quantum Monte Carlo simulations of polarons in one dimension.

When the material phases exhibit topological quantum numbers, they host defects protected by the nontrivial topology. Magnetic skyrmions are such “quantized” objects, and although many of them are metals, they had been most likely treated in theories as purely classical spin states. Here, we show that the electrons described by the Hubbard model with strong spin-orbit couplings can exhibit various nano- or flake-size skyrmions in their ground state. Importantly, the conducting electrons forming Fermi pockets themselves carry textured magnetic moments in both real and momentum space and on top of that possess Chern numbers in their energy bands. This quantum and conducting skyrmion is related to small skyrmions observed in atomic-layered compounds. We clarify how the effective magnetic interactions and magnetic anisotropies are tied to the spin-orbit coupling, and how they influence the stability of skyrmions beyond the phenomenology.

In this paper we present a concrete example comparing the results predicted by non-Hermitian quantum mechanics with those of a more comprehensive description that considers environment-induced fluctuations. Our results highlight inaccuracies in the non-Hermitian model. Specifically, we investigate the non-Hermitian skin effect and sensor in the Hatano-Nelson model, contrasting it with a more precise Lindblad description. Our analysis reveals that these phenomena can undergo breakdown when environmental fluctuations come to the forefront, resulting in a nonequilibrium phase transition from a localized skin phase to a delocalized phase. Beyond this specific case study, we engage in a broader discussion regarding the interpretations and implications of non-Hermitian quantum mechanics. This examination serves to broaden our understanding of these phenomena and their potential consequences.

We present an expression for the spectral gap, opening up new possibilities for performing and accelerating spectral calculations of quantum many-body systems. We develop and demonstrate one such possibility in the context of tensor network simulations. Our approach requires only minor modifications of the widely used simple update method and is computationally lightweight relative to other approaches. We validate it by computing spectral gaps of the 2D and 3D transverse-field Ising models and find strong agreement with previously reported perturbation theory results.

Electron spin resonance (ESR) spectroscopy in scanning tunneling microscopy (STM) has enabled probing the electronic structure of single magnetic atoms and molecules on surfaces with unprecedented energy resolution, as well as demonstrating coherent manipulation of single spins. Despite this remarkable success, the field could still be greatly advanced by a more quantitative understanding of the ESR-STM physical mechanisms. Here, we present a theory of ESR-STM that quantitatively models not only the ESR signal itself, but also the full background tunneling current, from which the ESR signal is derived. Our theory is based on a combination of Green's function techniques to describe the electron tunneling and a quantum master equation for the dynamics of the spin system along with microwave radiation interacting with both the tunneling current and the magnetic system. We show that this theory is able to quantitatively reproduce the experimental results for a spin-1/2 system (TiH molecules on MgO) across many orders of magnitude in tunneling current, providing access to the relaxation and decoherence rates that govern the spin dynamics due to intrinsic mechanisms and to the applied bias voltage. More importantly, our work establishes that (i) sizable ESR signals, which are a measure of microwave-induced changes in the junction magnetoresistance, require surprisingly high tip spin polarizations, and (ii) the coupling of the magnetization dynamics to the microwave field gives rise to the asymmetric ESR spectra often observed in this spectroscopy. Additionally, our theory provides very specific predictions for the dependence of the relaxation and decoherence times on the bias voltage and the tip-sample distance. Finally, with the help of electromagnetic simulations, we find that the transitions in our ESR-STM experiments, in which the tunnel junction is irradiated by a nearby microwave antenna, can be driven by the ac magnetic field at the junction.

We investigate the electronic Raman scattering of ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$ using a material-realistic dynamical mean-field theory approach. We identify the low-energy Fermi liquid behavior and point out that the enhanced Raman response at higher energies is a fingerprint of Hund metals. These signatures originate in the two-stage coherence of Hund metals and associated quasiparticle “unrenormalization.” In agreement with recent experimental observations, we find the ${\mathrm{B}}_{1g}$ and ${\mathrm{B}}_{2g}$ responses differ, but our calculations suggest a novel interpretation of this dichotomy. The ${\mathrm{B}}_{1g}$ response is dominated by the $xy$ orbital and the ${\mathrm{B}}_{2g}$ response receives contributions from all orbitals and is strongly affected by previously unnoticed finite-frequency interband nesting. We calculate the vertex-corrections to Raman response and show that their effect is nonvanishing but small.

The resistivity of two-dimensional (2D) metals generally exhibits insensitivity to electron-electron scattering. However, it is worth noting that Galilean invariance may not hold true in systems characterized by a spectrum containing multiple electronic branches or in scenarios involving electron-hole plasma. In the context of this paper, we focus on 2D electrons confined within a triple quantum well (TQW) based on HgTe. This system displays a coexistence of energy bands featuring both linear and paraboliclike spectra at low energy and, therefore, lacks the Galilean invariance. This paper employs a combined theoretical and experimental approach to investigate the transport properties of this two-component system across various regimes. By manipulating carrier density and temperature, we tune our system from a fully degenerate regime, where resistance follows a temperature-dependent behavior proportional to $T^2$ to a regime where both types of electrons adhere to Boltzmann statistics. In the nondegenerate regime, electron interactions lead to resistance that is weakly dependent on temperature. Notably, our experimental observations closely align with the theoretical predictions derived in this paper. In this paper, we establish the HgTe-based TQW as a promising platform for exploring different interaction-dominant scenarios for the massless-massive Dirac system.

We investigate the effect of structural deformation on the magnetic properties of orthorhombic ${\mathrm{CePdAl}}_3$ in relation to its tetragonal polymorph. Utilizing x-ray and neutron diffraction, we establish that the crystal structure has the $Cmcm$ space-group symmetry and exhibits pseudotetragonal twinning. According to density functional calculations, the tetragonal-orthorhombic deformation mechanism has its grounds in the relatively small free enthalpy difference between the polymorphs, allowing either phase to be quenched, and fully accounts for the twinned microstructure of the orthorhombic phase. Neutron diffraction measurements show that orthorhombic ${\mathrm{CePdAl}}_3$ establishes long-range magnetic order below $T_{\mathrm{N}}=5.29\left(5\right)$ K characterized by a collinear, antiferromagnetic arrangement of magnetic moments. Magnetic anisotropies of orthorhombic ${\mathrm{CePdAl}}_3$ arise from strong spin-orbit coupling as evidenced by the crystal-field splitting of the $4f$ multiplet, fully characterised with neutron spectroscopy. We discuss the potential mechanism of frustration posed by antiferromagnetic interactions between nearest neighbors in the tetragonal phase, which hinders the formation of long-range magnetic order in tetragonal ${\mathrm{CePdAl}}_3$. We propose that orthorhombic deformation releases the frustration and allows for long-range magnetic order.

We analyze a bubble-forming system composed of particles with competing long-range repulsive and short-range attractive interactions driven over a quasi-one-dimensional periodic substrate. We find various pinned and sliding phases as a function of substrate strength and drive amplitude. When the substrate is weak, a pinned bubble phase appears that depins elastically into a sliding bubble lattice. For stronger substrates, we find anisotropic bubbles, disordered bubbles, and stripe phases. Plastic depinning occurs via the hopping of individual particles from one bubble to the next in a pinned bubble lattice, and as the drive increases, there is a transition to a state where all of the bubbles are moving but are continuously shedding and absorbing individual particles. This is followed at high drives by a moving bubble lattice in which the particles can no longer escape their individual bubbles. The transition between the plastic and elastic sliding phases can be detected via signatures in the velocity-force curves, differential conductivity, and noise. When the bubbles shrink due to an increase in the attractive interaction term, they fit better inside the pinning troughs and become more strongly pinned, leading to a reentrant pinning phase. For weaker attractive terms, the size of the bubbles becomes greater than the width of the pinning troughs and the depinning becomes elastic with a reduced depinning threshold.