Localization may survive in periodically driven (Floquet) quantum systems, but is generally unstable for aperiodic drives. In this Letter, we identify a hidden conservation law originating from a chiral symmetry in a disordered spin-$\frac{1}{2}$ XX chain. This protects indefinitely long-lived localization for general—even aperiodic—drives. Therefore, rather counterintuitively, adding further potential disorder which spoils the conservation law delocalizes the system, via a controllable parametrically long-lived prethermal regime. This provides an example of persistent single-particle “localization without eigenstates.”

We present detailed studies of the superconductivity in high-pressure ${\mathrm{H}}_3\mathrm{S}$. X-ray diffraction measurements show that cubic $Im\overline{3}m {\mathrm{H}}_3\mathrm{S}$ was synthesized from elemental sulfur and hydrogen donor ammonia borane (${\mathrm{NH}}_3{\mathrm{BH}}_3$). Our electrical transport measurements confirm superconductivity with a transition temperature $T_c=197\mathrm{K}$ at $153\mathrm{GPa}$. From the analysis of both the normal-state resistivity and the slope of the critical field, we conclude that the superconductivity is described by clean-limit behavior. A significant broadening of the resistive transition in finite magnetic field is found, as expected for superconductors. We identify a linear temperature-over-field scaling of the resistance at the superconducting transition which is not described by existing theories.

We have investigated the high-frequency magnetoresistance of Kondo semiconductor ${\mathrm{SmB}}_6$ under ultrahigh magnetic fields generated by the electromagnetic flux-compression technique. The semiconductor-metal transition due to closing of the hybridization charge gap was observed at approximately 180 T. The critical magnetic field observed is substantially higher than that reported previously. At temperatures below around 10 K, another transition was observed at a lower field (approximately 80 T). We suggest that the observed 80-T transition relates with the energy scale of quasiparticles such as the spin polaron in the in-gap state.

We study how a population of spin waves can be characterized from the analysis of the electrical microwave noise delivered by an inductive antenna placed in its vicinity. The measurements are conducted on a synthetic antiferromagnetic thin stripe covered by a micron-sized antenna that feeds a spectrum analyzer after amplification. The antenna noise contains two contributions. The population of incoherent spin waves generates a fluctuating field that is sensed by the antenna: this is the “magnon noise.” The antenna noise also contains the contribution of the electronic fluctuations: the Johnson-Nyquist noise. The latter depends on all impedances within the measurement circuit, which includes the antenna self-inductance. As a result, the electronic noise contains information about the magnetic susceptibility of the stripe, though it does not inform on the absolute amplitude of the magnetic fluctuations. For micrometer-sized systems at thermal equilibrium, the electronic noise dominates and the pure magnon noise cannot be determined. If in contrast the spin wave bath is not at thermal equilibrium with the measurement circuit, and if the spin wave population can be changed then one could measure a mode-resolved effective magnon temperature provided specific precautions are implemented.

It has been proposed that the superconducting transition temperature $T_{\text{c}}$ of an unconventional superconductor with a large pairing scale but strong phase fluctuations can be enhanced by coupling it to a metal. However, the general efficacy of this approach across different parameter regimes remains an open question. Using the dynamical cluster approximation, we study this question in a system composed of an attractive Hubbard layer in the intermediate coupling regime, where the magnitude of the attractive Coulomb interaction $\left|U\right|$ is slightly larger than the bandwidth $W$, hybridized with a noninteracting metallic layer. We find that while the superconducting transition becomes more mean-field-like with increasing interlayer hopping, the superconducting transition temperature $T_{\text{c}}$ exhibits a nonmonotonic dependence on the strength of the hybridization $t_{\perp }$. This behavior arises from a reduction of the effective pairing interaction in the correlated layer that outcompetes the growth in the intrinsic pair-field susceptibility induced by the coupling to the metallic layer. We find that the largest $T_{\text{c}}$ inferred here for the composite system is comparable to the maximum value currently estimated for the isolated negative-$U$ Hubbard model.

Recent advances in theory and experiment declare the rare-earth (RE) hydrogen-rich compound $\mathrm{La}{\mathrm{H}}_{10}$ is a near room-temperature superconductor under high pressure. To understand the underlying mechanism of superconductivity and explore the crucial role of lanthanides in forming the RE-based polyhydrides, we here perform a theoretical study on the structural phase transition and superconductivity of late lanthanide ytterbium (Yb) metal under high pressure up to 240 GPa. Two alternative structures, $R\overline{3}m$ and $I4/mmm$ phases, of Yb are presented. Most interestingly, the $P{6}_3/mmc$ phase of Yb is serendipitously discovered to be a superior superconductor with a critical temperature value of 19.5 K at 160 GPa, which is higher than other known RE elemental superconductors. The present findings establish an alternative structural phase transition sequence of Yb, which offers insights for further understanding the vital physics mechanisms of a lanthanide-based superconductor.

So far nanoscale topological polar structures have been mainly observed in ferroelectric superlattices, nanodots, and complex heterostructures, originating from the intricate interplay of built-in electric field, polarization, strain, and their gradient-related energies. However, solid substrates hinder the continuous strain manipulation of the ferroelectric topological textures. Recently, a breakthrough in fabricating freestanding films has demonstrated the possibility of continuous strain manipulation, but there has been little experimental or theoretical investigation of whether polar topological structures exist in freestanding films. Herein, by performing phase field simulation on ${\left(\mathrm{PbTi}{\mathrm{O}}_3\right)}_{20}/{\left(\mathrm{SrTi}{\mathrm{O}}_3\right)}_{10}$ freestanding bilayers, we observed the stabilized ferroelectric skyrmion bubbles in a ferroelectric layer. A thickness-dependent phase diagram indicates that the skyrmion bubbles exist when the ferroelectric layer is between eight and 30 unit cells. Meanwhile, we demonstrated that the uniaxial strain is an effective way to manipulate the skyrmion bubble in freestanding films, which not only induces consolidation and rearrangement of skyrmion bubbles, but also induces a phase transition from the topological skyrmion bubble state to a standard $a_1/a_2$ domain state. These results provide us guidance with a mechanical approach to control topological polar structures in freestanding films.

The energy spectrum of bosonic excitations from a condensate is given by the spectrum of a non-Hermitian Hamiltonian constructed from a bosonic Bogoliubov–de Gennes (BdG) Hamiltonian in general even though the system is essentially Hermitian. In other words, two types of non-Hermiticity can coexist: one from the bosonic BdG nature and the other from the open quantum nature. In this paper, we propose boundary-dependent dynamical instability. We first define the bosonic dissipative BdG Hamiltonian in terms of Green's function in Nambu space and discuss the correct particle-hole symmetry of the corresponding non-Hermitian Hamiltonian. We then construct a model of the boundary-dependent dynamical instability so that it satisfies the correct particle-hole symmetry. In this model, an anomalous term that breaks the particle number conservation represents the non-Hermiticity of the BdG nature, while a normal term is given by a dissipative Hatano-Nelson model. Thanks to the competition between the two types of non-Hermiticity, the imaginary part of the spectrum can be positive without the help of the amplification of the normal part and the particle-hole band touching that causes the Landau instability. This leads to the boundary-dependent dynamical instability under the non-Hermitian skin effect—strong dependence of spectra on boundary conditions for non-Hermitian Hamiltonians—of the Bogoliubov spectrum.

${\mathrm{EuFe}}_2{\left({\mathrm{As}}_{1-x}{\mathrm{P}}_x\right)}_2$ hosts complex dynamical processes resulting from the interplay of its two electronic ground states, i.e., ferromagnetism and superconductivity. A detailed understanding of the observed dynamics is, however, still missing. In this sense, frequency-resolved experimental techniques can be crucial to disentangle the magnetic and/or superconducting origin of the phenomenology and to contribute to its modeling. Here, we report on the investigation of ${\mathrm{EuFe}}_2{\left({\mathrm{As}}_{0.7}{\mathrm{P}}_{0.3}\right)}_2$ based on muon-spin spectroscopy and ac magnetic susceptibility ($\chi$) measurements. The dependence of the internal field at the muon site on temperature is indicative of ferromagnetic ordering for the ${\mathrm{Eu}}^{2+}$ magnetic moments and only the conventional magnon scattering governs the longitudinal relaxation rate at low temperatures. At the same time, we observe a rich phenomenology for the imaginary component of the susceptibility ${\chi }^{″}$ by means of both standard ac susceptibility and a technique based on a microwave coplanar waveguide resonator. In particular, we detect activated trends for several features in ${\chi }^{″}$ over frequencies spanning ten orders of magnitude. To explain our results, we propose a model for the complex dynamics of vortices and antivortices influenced by the underlying structure of magnetic Meissner domains based on the identification of intra and interdomain depinning processes.

We study the Hubbard model with time-reversal-invariant flux and spin-orbit coupling and position-dependent onsite energies on the kagome lattice, using numerical and analytical methods. In particular, we perform calculations using real-space dynamical mean-field theory (R-DMFT). To study the topological properties of the system, we use the topological Hamiltonian approach. We obtain a rich phase diagram: For weak and intermediate interactions, depending on the model parameters, the system is in the band insulator, topological insulator, or metallic phase, while for strong interactions the system is in the Mott insulator phase. We also investigate the magnetic phases that occur in this system. For this purpose, in addition to R-DMFT, we also use two analytical methods: perturbation theory for large interactions and onsite energies and stochastic mean-field theory.

Quantum oscillations in the magnetic torque for the topological nodal-line semimetal NaAlSi with a superconducting transition at $T_{\mathrm{c}}=7\mathrm{K}$ have been measured to investigate the Fermi surface. Four oscillation branches, α, β, γ, and δ are observed, whose frequency ranges from 40 to 380 T in magnetic fields parallel to the $c$ axis. The results are consistent with the present first-principles band calculations, showing the presence of small Fermi surfaces elongated in the $k_z$ direction. We obtain the large mass enhancement factors 2.0 for α and 3.1 for γ, ascribed to many-body effects likely responsible for the superconductivity. A nontrivial Berry phase is obtained for α, arising from the linear dispersion of the energy band.

Higher-pseudospin fermions, associated with multiple band crossings in topological semimetals, are condensed matter analogs of higher-spin fermions in high-energy physics. In this paper, we demonstrate that analyzing the response of a circular drive is an effective way to detect the topology of the lowest-energy Bloch band, as it can be connected to a frequency-dependent probe. The response exhibits circular dichroism due to the differential excitation rates by the left- and right-circular orientations of a time-periodic drive, induced on a filled band, because of the geometrical properties of the Bloch bands. Our analytical approximation reveals that the dichroic response is quantized for isotropic systems, when the frequency of the drive is above a critical value, and thus correctly infers the ground-state Chern number. We demonstrate this through explicit numerical computations by considering three kinds of semimetals with pseudospin values of 1/2, 1, and 3/2, respectively, and all having linear dispersions. Furthermore, we investigate the effects of tilt and anisotropy on the systems, and find that although tilt does not have any effect on the response, the presence of anisotropy can drastically hamper the quantization. Our scheme thus provides an important methodology for designing future experiments to detect the topology of band structures.

Tensor product states have proved extremely powerful for simulating the area-law entangled states of many-body systems, such as the ground states of gapped Hamiltonians in one dimension. The applicability of such methods to the dynamics of many-body systems is less clear: The memory required grows exponentially in time in most cases, quickly becoming unmanageable. New methods reduce the memory required by selectively discarding/dissipating parts of the many-body wave function which are expected to have little effect on the hydrodynamic observables typically of interest: For example, some methods discard fine-grained correlations associated with $n$-point functions, with $n$ exceeding some cutoff ${\ell }_{*}$. In this paper, we present a theory for the sizes of backflow corrections, i.e., systematic errors due to discarding this fine-grained information. In particular, we focus on their effect on transport coefficients. Our results suggest that backflow corrections are exponentially suppressed in the size of the cutoff ${\ell }_{*}$. Moreover, the backflow errors themselves have a hydrodynamical expansion, which we elucidate. We test our predictions against numerical simulations run on random unitary circuits and ergodic spin chains. These results lead to the conjecture that transport coefficients in ergodic diffusive systems can be captured to a given precision $\epsilon$ with an amount of memory scaling as $exp\left[\mathcal{O}(log{\left(\epsilon \right)}^2)\right]$, significantly better than the naive estimate of memory $exp\left[\mathcal{O}\left(\mathrm{poly}\left({\epsilon }^{-1}\right)\right)\right]$ required by more brute-force methods.

Unraveling the dominant charge transport mechanism in high-mobility amorphous oxide semiconductors is still a matter of controversy. In the present study we extended the random band-edge model suggested before for the charge transport and Hall-effect mobility in such disordered materials [Fishchuk et al., Phys. Rev. B 93, 195204 (2016)], and also describe the field-effect-modulated thermoelectricity in amorphous In-Ga-Zn-O ($a$-IGZO) films under the same premises. The model is based on the concept of charge transport through the extended states and assumes that the transport is limited by the spatial variation of the position of the band edge due to the disorder potential, rather than by localized states. The theoretical model is formulated using the effective medium approximation framework and describes well basic features of the Seebeck coefficient in disordered materials as a function of energy disorder, carrier concentration, and temperature. Carrier concentration dependencies of power factor and thermoelectric figure of merit have been also considered for such systems. Besides, our calculations reveal a remarkable turnover effect from a negative to a positive temperature dependence of Seebeck coefficient upon increasing carrier concentration. The suggested unified model provides a good quantitative description of available experimental data on the Seebeck coefficient and the charge mobilities measured in the same $a$-IGZO transistor as a function of the gate voltage and temperature by considering the same charge transport mechanisms. This promotes a deeper understanding and a more credible and accurate description of the transport process in $a$-IGZO films.

Deformation behavior of multiphase aggregates has great significance for materials design and understanding the dynamics of the Earth. Here we studied the deformation of zircon (${\mathrm{ZrSiO}}_4$)-MgO aggregates and found that the introduction of MgO reduced overall deviatoric stress in the aggregates and thus controlled deformation mechanisms of the zircon phase. Zircon primarily deforms by a dominant $\left\{101\right\}\langle 10-1\rangle$ slip; however, activity of zircon $\left\{100\right\}\langle 010\rangle$ slip increases with the introduction of an increased ratio of MgO into the aggregates, as suggested by the experiments and simulations. We also found both zircon and MgO in the aggregates retained strong deformation texture, which is likely related to the symmetric variants of the dominant slip system of the hard zircon phase. Our results help to clarify the discrepancies in previous studies and understand which phase may dominate the seismic anisotropy in geosciences.

Low-dimensional quasiperiodic systems exhibit localization transitions by turning all quantum states localized after a critical quasidisorder. While certain systems with modified or constrained quasiperiodic potential undergo multiple localization transitions in one dimension, we predict an emergence of multiple localization transitions without directly imposing any constraints on the quasiperiodic potential. By considering a one-dimensional system described by the Aubry-André model, we show that an additional staggered on-site potential can drive the system through a series of localization transitions as a function of the staggered potential. Interestingly, we find that the number of localization transitions strongly depends on the strength of the quasiperiodic potential. Moreover, we obtain the signatures of these localization transitions in the expansion dynamics and propose an experimental scheme for their detection in the quantum gas experiment.

We study the pairing instability of a two-dimensional metallic system induced by Ising-nematic quantum fluctuations in the presence of an unavoidable relevant coupling of the nematic order parameter to the elastic modes (acoustic phonons) of the lattice. We find that this nematoelastic coupling ${\lambda }_{\mathrm{latt}}$ leads to a decrease of both the superconducting (SC) critical temperature $T_c$ and the gap function $\mathrm{\Delta }$, regardless of the gap symmetry. Interestingly, we show that ${\lambda }_{\mathrm{latt}}$ provides a knob that allows us to investigate the emergence of the SC phase at low temperatures, as an instability from either a non-Fermi liquid or a Fermi liquid normal state. The phase transitions between the SC and these normal states are characterized by different critical exponents, which may also vary for each gap symmetry. Finally, we argue that these results might explain the dependence of $T_c$ in the vicinity of the nematic quantum critical point exhibited by the compound ${\mathrm{FeSe}}_{1-x}{\mathrm{S}}_x$.

Realizing and characterizing interacting topological phases in synthetic quantum systems is a formidable challenge. Here, we propose a Floquet protocol to realize the antiferromagnetic Heisenberg model with power-law decaying interactions. Based on analytical and numerical arguments, we show that this model features a quantum phase transition from a liquid to a valence bond solid that spontaneously breaks lattice translational symmetry and is reminiscent of the Majumdar-Ghosh state. The different phases can be probed dynamically by measuring the evolution of a fully dimerized state. We moreover introduce an interferometric protocol to characterize the topological excitations and the bulk topological invariants of the interacting many-body system.

We consider the polarization function $P_Z^{\exp }\left(t\right)$ measured by the muon-spin relaxation ($\mu \mathrm{SR}$) technique for the ${\mathrm{SrCr}}_8{\mathrm{Ga}}_4{\mathrm{O}}_{19}$ and ${\mathrm{ZnCu}}_3{\left(\mathrm{OH}\right)}_6{\mathrm{Cl}}_2$ spin-liquid systems. We show the functional form of $P_Z^{\exp }\left(t\right)$ to imply that, in the temperature range of order 0.1 K, the spectral-weight function $F\left(\omega \right)$ of the magnetic correlations scales with $1/{\left|\omega \right|}^{1-x}$ ($0<x<1$) in the energy range of $\hslash \omega \approx 1\mu \mathrm{eV}$. We derive the parameters involved in $F\left(\omega \right)$ from fits to available experimental data. Inelastic neutron scattering data probing $F\left(\omega \right)$ in the millielectronvolt energy range are consistent with a more conventional behavior. These differences could be due to a variety of spin-dynamics mechanisms, i.e., intrinsic to the kagome layer or related to the magnetic defects that have been evidenced in these compounds, acting at different energies. New $\mu \mathrm{SR}$ measurements are proposed and theoretical developments are suggested to pinpoint the mechanisms at play.