Charge carrier mobilities are critical parameters in halide perovskite solar cells, governing their average carrier velocity under an applied electric field and overall efficiency. Recent advances in first-principles calculations of electron-phonon interactions and carrier mobilities have enabled predictive computations for perovskite solar cells. However, the flexible octahedral frameworks and cationic displacements in these materials challenge the harmonic approximation, leading to significant difficulties in accurately calculating transport properties. To address these issues, we combine temperature-dependent effective potentials with the ab initio Boltzmann transport equations to compute carrier mobilities in a representative lead-free perovskite, ${\mathrm{CsSnBr}}_3$. At room temperature, the electron (hole) Hall mobilities in ${\mathrm{CsSnBr}}_3$ are 106 (256) ${\mathrm{cm}}^2/\left(\mathrm{Vs}\right)$ when neglecting anharmonic effects and 59 (145) ${\mathrm{cm}}^2/\left(\mathrm{Vs}\right)$ when included. This overestimation of the harmonic approximation arises from the neglect of scattering coming from soft modes. We provide a workflow for performing first-principles carrier mobility calculations in anharmonic systems, advancing the predictive modeling of perovskite solar cells.

We study the dissipative dynamics of a class of interacting “gamma-matrix” spin models coupled to a Markovian environment. For spins on an arbitrary graph, we construct a Lindbladian that maps to a non-Hermitian model of free Majorana fermions hopping on the graph with a background classical ${\mathbb{Z}}_2$ gauge field. We show, analytically and numerically, that the steady states and relaxation dynamics are qualitatively independent of the choice of the underlying graph, in stark contrast to the Hamiltonian case. We also show that the exponentially many steady states provide a concrete example of mixed-state topological order, in the sense of strong-to-weak spontaneous symmetry breaking of a one-form symmetry. While encoding only classical information, the steady states still exhibit long-range quantum correlations. Afterward, we examine the relaxation processes toward the steady state by numerically computing decay rates, which we generically find to be finite, even in the dissipationless limit. However, we identify symmetry sectors where fermion-parity conservation is enhanced to fermion-number conservation, where we can analytically bound the decay rates and prove that they vanish in the limits of both infinitely weak and infinitely strong dissipation. Finally, we show that while the choice of coherent dynamics is very flexible, exact solvability strongly constrains the allowed form of dissipation. Our work establishes an analytically tractable framework to explore nonequilibrium quantum phases of matter and the relaxation mechanisms toward them.

We identify a universal functional form that governs anticoncentration in random quantum circuits—one that holds across diverse circuit architectures and depths, and crucially remains valid even at finite system sizes and shallow depth. We support this claim through analytical results for ensembles of random tensor-network states and random-phase models. This compact, universal expression for the output bitstring probability distribution is fully characterized by just two fitting parameters, as validated through extensive numerical simulations. Our findings underscore the pivotal role of finite-size and finite-depth effects in shaping anticoncentration, and they introduce a practical framework for benchmarking quantum devices using shallow circuits, thereby enabling validation of systems significantly larger than previously accessible.

We report time-domain measurements of indirectly coupled resonators in open systems. We examine a coupled LRC circuit and a cavity-magnon-polariton system, each with resonators coupled through a shared transmission line. In both cases, time-domain measurements directly resolve the temporal evolution of hybridized eigenmodes, thereby revealing non-Hermitian dynamics. To unify the platforms, we formulate a general model that uses circuit analysis and temporal coupled-mode theory and derive the corresponding S-parameter expressions. Moreover, recent theoretical work has shown that frequency-domain absorption is more effective than transmission for identifying eigenmodes in open systems. Our work provides an experimental confirmation of this prediction which agrees with the direct time-domain observations.

We investigate the quantum Mpemba effect (QME) in isolated, nonintegrable quantum systems, where relaxation dynamics depend on structure of the initial states. By analyzing the distribution of initial states across symmetrical subspaces, we identify a tunable mechanism that influences the emergence of QME, showing faster relaxation from certain out-of-equilibrium states. Additionally, we propose an experimentally realizable quantum circuit, which requires no complex controls on quantum simulator platforms and serves to verify our theoretical predictions. These results establish symmetry-resolved state engineering as a practical tool for manipulating nonequilibrium quantum dynamics.

In this work, we use a mixed quantum-classical (mean-field) many-body approach for simulating the quantum dynamics of excitons and exciton polaritons beyond the single-excitation subspace. We combine the multitrajectory Ehrenfest approach, which propagates slow degrees of freedom classically, with the Gross-Pitaevskii method, which propagates fast degrees of freedom in a mean-field fashion. We use this mean-field many-body Ehrenfest approach to analyze how the phonon-induced dynamic disorder and the many-body interaction affect the incoherent and coherent dynamics of excitons and exciton polaritons. We examine how the number of excitations and the strength of repulsive exciton-exciton interaction nonlinearly influence the transport, Fröhlich scattering, and decoherence.

The high thermal sensitivity of upconversion nanoparticles (UCNPs) luminescence at the nanoscale enables precise and rapid temperature detection, advancing nano-thermometry applications in quantum optics, catalytic reactions, and nanophotonics. Here, the phonon-assisted upconversion luminescence with a high thermal sensitivity is achieved by rare-earth doped UCNPs (${\mathrm{NaYF}}_4:{\mathrm{Yb}}^{3+}/{\mathrm{Er}}^{3+}$) in vacuum optical tweezers. We found that an essential contribution of phonon-assisted luminescence processes leading to high thermal sensitivity is not only from increasing the absorption cross section of ${\mathrm{Yb}}^{3+}$ but also from facilitating efficient energy transfer from ${\mathrm{Yb}}^{3+}$ to ${\mathrm{Er}}^{3+}$ ions. The increase in thermal sensitivity with the number of phonons involved in the progress of phonon-assisted luminescence can be well described by the temperature-dependent phonon population model. The study reveals how phonon-assisted processes influence thermal sensitivity in UCNPs, contributing to a deeper understanding of nanoscale temperature-dependent luminescence.

Attosecond extreme-ultraviolet (XUV) transient absorption spectroscopy measurements on the Peierls-distorted phase of the semimetal antimony (Sb) are presented. After excitation by an ultrashort, broad band near-infrared (NIR) pulse, the distortion is (partly) lifted causing the well-known coherent phonon motion of the lattice. While the overall observed dynamics generally follow a displacive excitation model, a delayed onset of the pump-induced carrier dynamics because of hot-carrier thermalization is observed, as well as a large spectral phase dependence in the coherent phonon oscillation. This is attributed to significantly different carrier relaxation timescales for carrier energies above and near the Fermi level of the semimetal and corroborated by a simple theoretical model that considers the carrier relaxation timescales in the displacive phonon model to explain the observed dynamics. Our results provide direct experimental evidence about the role of carrier-relaxation in the origin of displacive coherent phonon motion.

A thorough understanding of lattice dynamics, particularly how they couple with spin through spin-phonon interactions, is crucial for pioneering new spin-caloritronic applications. Despite extensive studies on ${\mathrm{Cr}}_2{\mathrm{O}}_3$, the origin of nonlinear thermal expansions and the unusual stiffening of optical phonon modes is still elusive. Through inelastic neutron scattering and atomistic calculations, we found that these behaviors can be attributed to the renormalization of electron states owing to the magnetic transition, and we ruled out the effects from thermal expansion, phonon anharmonicity, magnetostriction, or electron-phonon interactions. Importantly, our quantitative modeling suggests that the common belief that dynamic spin-phonon interactions are the origin of anomalous phonon energy stiffening in magnetic compounds does not apply in ${\mathrm{Cr}}_2{\mathrm{O}}_3$.

We address weak-coupling frictional sliding with phononic dissipation by means of analytic many-body techniques. Our model consists of a particle (the “slider”) moving through a two- or three-dimensional crystal and interacting weakly with its atoms, and therefore, exciting phonons. By means of linear response theory, we obtain explicit expressions for the friction force slowing down the slider as a function of its speed, and compare them to the friction obtained by simulations, demonstrating a remarkable accord.

High field magnetic resonance of nuclear spins is normally carried out at or near the Larmor frequency ${\mathrm{\Omega }}_0$. Here, we report an observation of nonsecular nuclear spin resonances far off ${\mathrm{\Omega }}_0$. These originate from nonsecular terms of the nuclear spin-spin interaction and provide means for the control of coupled two level systems. In systems of equivalent nuclear spins, nonsecular resonances were predicted to lead to anomalous, fast relaxation of the nuclear spin polarization. We report experimental results that are in excellent agreement with the predicted behavior.

Non-Hermitian physics is a rapidly growing field that hosts rich intriguing phenomena with broad applications in photonics, condensed matter, and quantum information science. Yet, it is still unclear how to properly deal with the nonadiabatic dynamics in a driven non-Hermitian quantum system. Here, we introduce a novel theoretical framework based on time-dependent biorthogonal quantum formalism by redefining the associated state to ensure gauge-independent transition probabilities. Applying this framework to a linearly driven non-Hermitian system, our approach reveals universal power-law scaling of defect production that is consistent with the Kibble-Zurek mechanism in the adiabatic regime at exceptional points. In the fast quench regime, universal scaling behaviors are also found, which can be explained by the adiabatic-impulse approximation. Moreover, upon trespassing the $\mathcal{PT}$-broken region, the phenomenon of defect freezing, i.e., violation of adiabaticity, is observed.

We use the eigenstate thermalization hypothesis to derive a quantum master equation for a system that is weakly coupled to a chaotic finite-sized bath prepared in a pure state. We show that the emergence of Markovianity is controlled by the spectral function of the ETH and that local detailed balance emerges in the Markovian regime for a broad class of pure bath states. We numerically verify this result by comparing the master equation to dynamics computed using exact diagonalization of a chaotic Hamiltonian. We also compare the master equation to exact dynamics for an integrable bath and find that at finite size they strongly disagree. Our work puts forward eigenstate thermalization as a foundation for open quantum systems theory, thus extending it beyond ensemble bath preparations to chaotic many-body environments in generic pure states.

We present a novel approach within the functional renormalization group framework for computing critical exponents that characterize the time evolution of out-of-equilibrium many-body systems. Our approach permits access to quantities involved in the renormalization procedure, using an expansion about time-translation invariant problems. This expansion can be upgraded to a fully time-dependent computation by iteration. As a prototypical example, we compute the aging exponent $\theta$ describing the dynamics of model A following a sudden quench to the critical point. Already at leading order, the approach demonstrates remarkable accuracy when compared with MC simulations and resummed perturbative expansions in the range $2<d<4$. This yields results that surpass those of the two-loop $\epsilon$ expansion in accuracy and match analytically known benchmarks at large $N$. These findings contribute to a deeper understanding of out-of-equilibrium universality and open new avenues for nonperturbative studies of critical dynamics, as well as for exploring the critical behavior of systems with spatial boundaries.

Diffusion is a ubiquitous phenomenon. It is a widespread belief that, if the area under a current autocorrelation function converges in time, the corresponding spatiotemporal density dynamics should be diffusive. This may be viewed as a result of the combination of linear response theory with the Einstein relation. However, attempts to derive this statement from first principles are notoriously challenging. We first present a counterexample by constructing a correlation function of some density wave, such that the area under the corresponding current autocorrelation function converges, but the dynamics do not obey a diffusion equation. Then we introduce a method based on the recursion method and the Mori memory formalism that may help to identify diffusion. For a decisive answer, one would have to know infinitely many so-called Lanczos coefficients, which is unattainable in most cases. However, in the examples examined in this paper, we find that the practically computable number of Lanczos coefficients suffices for a strong guess.

Recent studies have shown some unusual nonlinear dispersion behaviors that are disconnected from the linear regime. However, existing analytical techniques, such as perturbation methods, fail to correctly capture these behaviors. Here I propose an equivalent eigenvalue approach that converts the nonlinear wave equation to an equivalent linear eigenvalue problem, which directly gives the nonlinear dispersion relation and modal vectors. The theoretical approach is employed to one-dimensional (1D) phononic chains and 2D hexagonal lattices with alternating softening and hardening nonlinearities, revealing amplitude-induced bandgap opening and closing phenomena. The theoretical results are validated via full-scale simulations with initial excitations and periodic boundary conditions, in which steady-state nonlinear plane wave responses are numerically obtained. Moreover, these nonlinear phenomena are leveraged to achieve tunable frequency splitting and focusing effects. Thus this work opens paradigms for understanding nonlinear wave physics and for achieving tunable wave control capabilities.

This paper experimentally investigates topologically protected edge modes in a water wave channel through a direct geometric mapping to the one-dimensional Su-Schrieffer-Heeger (SSH) model. By designing a periodic channel with alternating widths, we replicate the key features of the SSH model, leading to the emergence of robust zero-energy sloshing edge modes localized at the boundaries. Experimental data show excellent agreement with theoretical predictions, supported by two-dimensional numerical simulations. In the nonlinear regime, two distinct bifurcations are observed, indicating the appearance of secondary resonances. This study highlights the relevance of the SSH model for water-wave systems and provides an accessible method to explore topological edge states in classical wave systems.

The narrow band-gap semiconductor elemental tellurium (Te) has a unique electronic structure due to strong spin-orbit splitting and a lack of inversion symmetry of its helical lattice. Using broadband extreme ultraviolet core-level transient absorption, we simultaneously measure the coherently coupled photoinduced carrier and lattice dynamics at the Te ${\mathrm{N}}_{4,5}$ edge initiated by a few-cycle NIR pulse. Ultrafast excitation of carriers leads to a coherently excited $A_1$ phonon oscillation and the generation of a hot carrier population distribution that oscillates in temperature, and the phonon excursion and hot carrier temperature are $\pi$ out of phase with respect to each other. The depths of modulation suggest a significant coupling between the electronic and lattice degrees of freedom in Te. A long-lived shift of the absorption edge suggests an excited state of Te in another equilibrium potential energy surface that lives on the order of the carrier recombination timescale. The observed phonon-induced oscillations of the hot carriers are supportive of a change in the metallicity, whereby Te becomes more metallic with increasing phonon-induced displacement. Additionally, near the Fermi level we observe an energy-dependent phase of the displacive excitation of the $A_1$ phonon mode. The discovery of coherent coupling between the lattice and hot carriers in Te provides the basis to investigate coherent interactions between spin and orbital degrees of freedom. The results spectrally and temporally resolve the correlation between photoexcited hot carriers and coherent lattice excitations, providing insight on the optical manipulation of the Te electronic structure at high carrier densities exceeding ${10}^{21}{\mathrm{cm}}^{-3}$.

The local Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) quantum master equation is a powerful tool for the study of open quantum many-body systems. However, its microscopic derivation applicable to many-body systems is available only in limited cases, and it has yet to be fully understood under what microscopic conditions the local GKSL equation is valid. We derive the local GKSL equation on the basis of the Lieb-Robinson bound, which provides an upper bound of the propagation of information in a broad class of quantum many-body systems. We numerically test the validity of the derived local GKSL equation for a one-dimensional tight-binding fermion chain.

Floquet time crystals are characterized by the subharmonic behavior of temporal correlation functions. Studying the paradigmatic time crystal based on the disordered Floquet quantum Ising model, we show that its temporal spin correlations are directly related to spectral characteristics and that this relation provides analytical expressions for the correlation function of finite chains, which compare favorably with numerical simulations. Specifically, we show that the disorder-averaged temporal spin correlations are proportional to the Fourier transform of the splitting distribution of the pairs of eigenvalues of the Floquet operator, which differ by $\pi$ to exponential accuracy in the chain length. We find that the splittings are well described by a log-normal distribution, implying that the temporal spin correlations are characterized by two parameters. We discuss possible implications for the phase diagram of Floquet time crystals.