A Thouless pump is a slowly driven one-dimensional band insulator, which pumps charge at a quantized rate. Previous study showed that pumping persists in weakly disordered chains, and separately in clean chains at finite drive frequency. We study the interplay of disorder and finite frequency, and show that the pump rate always decays to zero because of nonadiabatic transitions between the instantaneous eigenstates. However, the decay is slow, occurring on a timescale that is exponentially large in the period of the drive. In the adiabatic limit, the band gap in the instantaneous spectrum closes at a critical disorder strength above which pumping ceases. We predict the scaling of the pump rate around this transition from a model of scattering between rare states near the band edges. Our predictions can be experimentally tested in ultracold atomic and photonic platforms.

Experimental data show that under pressure, Gd goes through a series of structural transitions $\mathrm{hcp}\to \mathrm{Sm}$-type (close-packed rhombohedral) $\to \mathrm{dhcp}$ that is accompanied by a gradual decrease of the Curie temperature and magnetization till the collapse of a finite magnetization close to the dhcp structure. We explore theoretically the pressure-induced changes of the magnetic properties, by describing these structural transitions as the formation of fcc stacking faults. Using this approach, we are able to describe correctly the variation of the Curie temperature with pressure, in contrast to a static structural model using the hcp structure.

While the transition between skyrmionic and nontopological states has been widely explored as a bit operation for information transport and storage in spintronic devices, the ultrafast dynamics of such transitions remains challenging to observe and understand. Here, we utilize spin-dynamics simulations and harmonic transition state theory (HTST) to provide an in-depth analysis of the nucleation of skyrmionic states in helimagnets. We reveal a persistent blinking (creation-annihilation) phenomenon of these topological states under specific conditions near the phase boundary between skyrmion and conical states. Through a minimum-energy path analysis, we elucidate that this blinking behavior is favored by the formation of chiral bobber (CB) surface states and that the collapse of CBs differs from that of skyrmions in thin films due to their different oscillation modes. We further employ HTST to estimate the typical blinking time as a function of the applied magnetic field and temperature. Finally, we illustrate the practical use of skyrmion blinking for controlled probabilistic computing, exemplified by a skyrmion-based random-number generator.

An electronic spin-fluctuation theory of temperature-driven spin-reorientation transitions (SRTs) in transition-metal nanostructures is formulated in the framework of a realistic $d$-band model Hamiltonian including hybridizations, intra-atomic Coulomb interactions and spin-orbit coupling. Using the Hubbard-Stratonovich functional-integral transformation in the static approximation and the virtual crystal alloy analogy, we determine the temperature dependence of the magnetic anisotropy free energy $\mathrm{\Delta }{F}_{\delta \gamma }=F_{\delta }-F\gamma$ in a nonperturbative way, as the difference between the electronic free energies for different magnetization directions $\delta$ and $\gamma$. The results for an Fe monolayer show, in qualitative agreement with experiments, that a transition from off-plane magnetization ($\delta =z$) to in-plane magnetization ($\gamma =x$) takes place at a relatively low temperature $T_{\mathrm{SR}}\simeq 0.3T_{\mathrm{C}}$, where $T_{\mathrm{C}}$ refers to the film Curie temperature. A remarkable correlation is observed between $\mathrm{\Delta }{F}_{zx}\left(T\right)$ and the anisotropy $\mathrm{\Delta }{m}_{xz}^L\left(T\right)=\langle L_x\rangle -\langle L_z\rangle$ of the average orbital moment $\langle L_{\delta }\rangle$ as a function of temperature $T$, the easy axis corresponding to the magnetization direction $\delta$ yielding the largest $\langle L_{\delta }\rangle$. The microscopic origin of the SRT is revealed by identifying the various energy and entropy contributions to $\mathrm{\Delta }{F}_{zx}\left(T\right)$. At very low temperatures the magnetic anisotropy energy $\mathrm{\Delta }{E}_{zx}=E_z-E_x$ favors the perpendicular magnetization direction. However, as $T$ increases, the magnetic anisotropy entropy $\mathrm{\Delta }{S}_{zx}=S_z-S_x$ rapidly decreases, mainly because of the contribution of electron-hole excitations. In this way a more modest decrease of $\mathrm{\Delta }{E}_{zx}$ is overridden, driving the temperature-induced reorientation transition to in-plane magnetization.

Control of quantum spin states of magnetic molecules on surfaces has been actively pursued for emergent exotic physics and potential technological applications. Co-phthalocyanine (CoPc) is a prototypical molecular magnet with a spin of 1/2, which has been shown to be too fragile when the molecule is adsorbed on good metals but can be preserved on the semimetallic Sb(111) substrate. Here, we use first-principles calculations to reveal that, counterintuitively, the spin of individual CoPc is also quenched on the semimetallic Bi(111) substrate, and the underlying reason is attributed to a significant elevation of the Fermi level close to the Co-$d_{z^2}$ orbital by the stronger spin-orbit coupling in bismuth. We further show that the molecular spin can be recovered via intermolecular coupling, accompanied by a topological phase transition from a quantum spin Hall state to a magnetic topological semimetal. Finally, we demonstrate that the spin state of CoPc is enhanced on the half-metallic $\mathrm{Cr}{\mathrm{O}}_2$(110) substrate, associated with reverse band alignment and charge transfer. Collectively, our comparative studies establish rich tunability of molecular spins on different metal substrates for future molecular spintronic and quantum information devices.

The discovery of nickelate superconductivity provided the first example of a non-copper-based material with superconductivity strongly analogous to the cuprates. However, recent findings raise questions and inconsistencies around the electron counts and doping phase diagrams. We show using superconducting ${\mathrm{La}}_4{\mathrm{Ni}}_3{\mathrm{O}}_{10}$ that there are unconventional interlayer and interorbital intrinsic doping effects that render the $d_{x^2-y^2}$ occupation similar to the cuprates. The results enable a consistent framework for nickelate superconductivity, while maintaining the connection between cuprate and nickelate superconductors.

Ferroelectric materials are great candidates for acousto-optic device applications due to their high figures of merit, low attenuation, and high optical birefringence. With the excellent lattice tunability of oxide membranes, it is possible to explore the tuning of the acousto-optic diffraction by applying uniaxial strain along any lattice orientation. Here, the elasto-optic effect of single-domain $\mathrm{BiFe}{\mathrm{O}}_3$ membranes under uniaxial strain has been studied using Mueller matrix ellipsometry at room temperature. By applying uniaxial tensile strain along the ${\left[110\right]}_p$ (pseudocubic) direction, the indices’ ellipsoid is rotated and deformed, showing opposite strain dependencies of refractive indices along different axes. The refractive index $n$ along the $[\overline{1}\overline{1}2{]}_p$ direction increases with tensile strain and the corresponding elasto-optic coefficient $p$ exhibits a remarkably large value of 0.89. Our work demonstrates the effective engineering of refractive indices by applying uniaxial strain along selective lattice orientations, providing a different knob to design transition metal oxides for interesting optical properties.

We consider the resonance and scattering properties of a composite medium containing scatterers whose properties are modulated in time. When excited with an incident wave of a single frequency, the scattered field consists of a family of coupled harmonics at frequencies differing by the frequency of temporal modulation. Similarly, the temporal modulation induces coupling between the resonance frequencies, leading to exceptional points at certain modulation amplitudes. Moreover, the lack of energy conservation causes scattering coefficients to blow up when (complex) resonances cross the real axis. We have developed an integral operator approach to characterize the scattering problem and, for high-contrast scatterers, we present small-volume asymptotic formulas analogous to the classical results for the static (unmodulated) case. We conclude the paper with a boundary integral formulation of the time-modulated problem, which gives an efficient numerical approach and corroborates the asymptotic formulas.

According to x-ray diffraction (XRD) measurements, $\mathrm{PbTi}{\mathrm{O}}_3$ undergoes a phase transition from a tetragonal ferroelectric (FE) phase to a cubic paraelectric phase at 763 K. However, x-ray absorption fine-structure (XAFS) measurements indicate that $\mathrm{PbTi}{\mathrm{O}}_3$ is locally tetragonal even after the phase transition. The difference in these results is because XAFS measurements can probe local features of a structure, while XRD averages over such local features. For both measurements to be consistent, $\mathrm{PbTi}{\mathrm{O}}_3$ is macroscopically cubic but locally tetragonal after the phase transition. Despite this, most models, such as the Landau-Ginsburg-Devonshire theory and effective Hamiltonians, are still unable to explain this phenomenon. Moreover, these methods involve model parameters fitted to experimental or theoretical data and do not consider other tetragonal configurations, such as domain walls, to predict the phase transition. In our previous study, we used our zentropy approach to predict the phase transition by considering the tetragonal FE ground-state configuration and the tetragonal 90 ° and 180 ° domain wall configurations with their total energies at 0 K. In this paper, the Helmholtz energies of the three configurations are obtained from density functional theory calculations through energy-volume curves and phonon calculations. The predicted phase transition temperature using the meta-GGA $r^2\mathrm{SCAN}$ and revised multiplicities of configurations is 716 K, showing good agreement with the experimental value of 763 K.

We report a remarkable spectral phenomenon in a generic quantum lattice gas model. As the interaction strength increases, eigenstates spontaneously reorganize, leading to plateaus in the interaction energy. Gaps between plateaus can emerge similarly to continuous phase transitions. Our perturbation analysis indicates that, aside from these gaps, the plateau structure of the spectrum remains stable in the thermodynamic limit. The structured spectrum naturally manifests in far-from-equilibrium dynamics, exhibiting multiple stages. Our findings reveal a connection between emergent properties in high-energy states and equilibration dynamics in closed quantum systems, offering insights into the impact of interactions across the entire energy spectrum. These results directly relate to experiments probing equilibration in quantum spin systems and lattice gases.

Recent studies have demonstrated that the chemical reactivity of noble gas elements, such as Xe and He, increases significantly under high pressure, leading to the discovery of many unconventional compounds that are unstable under ambient conditions. In this paper, we propose three different and energetically stable compounds—${\mathrm{NH}}_5\mathrm{Xe}, {\mathrm{NH}}_{11}\mathrm{Xe}$, and ${\mathrm{NH}}_{13}\mathrm{Xe}$—through a combination of structural prediction methods and first-principles calculations. Our findings reveal that these compounds are dynamically stable and possess wide band gaps exceeding 4 eV, classifying them as insulators. Notably, the incorporation of xenon enhances the hydrogen content within the compounds, with ${\mathrm{NH}}_{11}\mathrm{Xe}$ and ${\mathrm{NH}}_{13}\mathrm{Xe}$ exhibiting the highest hydrogen storage capacities among the proposed compounds, reaching up to 44% and 48%, respectively. This positions them as promising candidates for advanced hydrogen storage materials. Furthermore, ab initio molecular dynamics simulations reveal that these compounds undergo phase transitions from solid to superionic and eventually to liquid as temperature increases. The stable pressure-temperature regions of the superionic and liquid phases align with the extreme conditions found in the interiors of Earth and icy planets (Uranus and Neptune), suggesting that these ${\mathrm{NH}}_x\text{−}\mathrm{Xe}$ compounds could be potential constituents of their mantles. These results not only provide the potential of ${\mathrm{NH}}_x\text{−}\mathrm{Xe}$ compounds in hydrogen storage but also offer distinct insights into the composition and behavior of materials under extreme conditions in planetary interiors.

Space-time inversion symmetry can generate intriguing types of spinless excitations in crystalline materials. Here, we propose a topological phase protected by space-time inversion symmetry—the crossed real nodal line (RNL) in the phonon spectrum of gold monobromide (AuBr). In AuBr, there exist four straight nodal lines, which are linked by a crossed nodal line formed by two lower bands. Remarkably, each adjacent two of the four straight nodal lines is a pair, forming a crossed RNL with nontrivial real Chern number. Such configuration and pairing mode of RNL have never been reported. The crossed RNL exhibits unique surface and hinge states distinguished from that of the conventional RNLs. The symmetry protection and the transformation under the symmetry-preserving strain of the crossed RNL are also investigated. Our results open the door to a new class of topological states and predict its realization in experimentally synthesized material.

Superconductors without inversion symmetry can exhibit a nonzero magnetization when a supercurrent is present, leading to nondissipative magnetoelectric effects. Here, we focus on understanding the relation between the spin and orbital properties of these effects in spin-singlet noncentrosymmetric superconductors with orbital Rashba coupling. Our findings indicate that the correlation between spin and orbital moments induced by supercurrents is generally not determined by the sign of atomic spin-orbit coupling but rather by the number of bands at the Fermi level and the orbital characteristics of those bands with respect to the mirror parity. The outcomes demonstrate that the sign change of the orbital Edelstein effect near avoiding crossing bands remains robust despite modifications to the atomic spin-orbit amplitude. Furthermore, we observe that the spin Edelstein effect is typically one order of magnitude smaller than the orbital Edelstein effect, but can be significantly enhanced in certain scenarios with increased atomic spin-orbit coupling.

We consider anyonic quasiparticles with charge $e/2$ described by the $\nu =1/2$ chiral Luttinger liquid, which collide in a Hong–Ou–Mandel-like interferometer. These colliding anyonic channels can be formally viewed as hosting Laughlin-like fractional $\nu =1/2$ quasiparticles. More specifically, two possible geometries are considered: (i) a two-edge-channel setup where anyons originate from equilibrium reservoirs; and (ii) a four-edge-channel setup where nonequilibrium anyons arrive at the collider in the form of diluted beams. For both setups, we calculate the tunneling current and the current correlations. For setup (i), our results provide analytically exact expressions for the tunneling current, tunneling-current noise, and cross-correlation noise. An exact relation between conductance and noises is explicitly demonstrated. For setup (ii), we show that the tunneling current and the generalized Fano factor [defined in B. Rosenow et al. (2016)] are finite for diluted streams of $\nu =1/2$ anyons. This is due to the processes where nonequilibrium anyons, supplied via either source edge, directly tunnel at the central QPC. Thus, to obtain meaningful results in this case, one should go beyond the so-called time-domain braiding processes, where nonequilibrium anyons do not tunnel at the collider, but rather indirectly influence the tunneling by braiding with the quasiparticle-quasihole pairs created at the collider. This suggests that the effect of direct tunneling and collisions of diluted anyons in the Hong-Ou-Mandel interferometer can be important for various observables in physical quantum-Hall edges at Laughlin filling fractions.

We present a generalized framework, renormalized density matrix downfolding (RDMD), to derive systematically improvable, highly accurate, and nonperturbative effective models from ab initio calculations. This framework moves beyond the common role of ab initio calculations as calculating the parameters of a proposed Hamiltonian. Instead, RDMD provides the capability to decide whether a given effective Hilbert space can be identified from the ab initio data and assess the relative quality of ansatz Hamiltonians. Any method of ab initio solution can be used as a data source, and as the ab initio solutions improve, the resultant model also improves. We demonstrate the framework in an application to the downfolding of a hydrogen chain to a spin model, in which we find the interatomic separations for which a nonperturbative mapping can be made even in the strong coupling regime where standard methods fail, and compute a renormalized spin model Hamiltonian that quantitatively reproduces the ab initio dynamics.

In this paper, ultrafast optical spectroscopy was employed to elucidate the intricate topological features of ${\mathrm{EuIn}}_2{\mathrm{As}}_2$, a promising candidate for a magnetic topological crystalline axion insulator. Our investigation has revealed the exceptional sensitivity of the ultrafast carrier dynamics to the antiferromagnetic phase transition ($T_N\approx 16$ K). Below $T_N$, two distinct, extremely low-energy collective modes, ${\omega }_1$ and ${\omega }_2$, with frequencies of $\sim 9.9$ and 21.6 GHz at $T=4$ K, respectively, were observed, exhibiting strong temperature dependence. The higher-frequency mode is a magnon, and the lower-frequency mode, whose origin is currently uncertain, cannot be attributed to a coherent acoustic phonon. Additionally, high-fluence photoexcitation suggests the possibility of light-induced nonthermal phase transitions, such as the disruption of antiferromagnetic order. These findings provide insights into the interplay between topology and magnetism in ${\mathrm{EuIn}}_2{\mathrm{As}}_2$, making it a promising candidate for applications in quantum information and spintronics.

This paper reports an extensive study of three-dimensional topological ordered phases that in one of the directions behave like usual topological order concerning mobility of excitations, but in the perpendicular plane manifest type-II fracton physics dictated by a fractal subsystem symmetry. We obtain an expression for the ground state degeneracy, which depends intricately on the sizes of the plane, signaling a strong manifestation of UV/IR mixing. The ground state degeneracy can be interpreted in terms of spontaneous/explicit breaking of fractal subsystem symmetries. We also study the boundary physics, which in turn is useful to understand the connection with certain two-dimensional phases. Finally, we derive a low-energy but not long-distance effective field theory, by Higgsing a fractal $U\left(1\right)$ symmetry and taking the deep IR limit. This description embodies in a natural way several aspects of the phases, such as the content of generalized global symmetries, the role of fractal symmetries on the mobility of excitations, the anomalies, and the boundary physics.

Electrons in a quantum Hall fluid can bind with an integer number of vortices to form composite fermions and composite bosons. We show that the quantum Hall bilayer at filling $\nu =\frac{1}{4}+\frac{3}{4}$ with interlayer separation $d$ can be well described in terms of these composite particles. At small $d$ the system can be understood as interlayer paired electrons and holes, whereas at large $d$ the system is best understood in terms of composite fermions with four vortices attached to each electron. By computing the overlaps of trial wave functions with the ground state from exact diagonalization, we find that, as $d$ increases, the number of vortices that attach to each electron increases. We also construct trial states for two types of excitation, the Goldstone mode and a meron excitation. These two trial states have good overlaps with the lowest excited states in the exact diagonalization spectrum for small and intermediate $d$, respectively.

Given a tripartite quantum state on $A,B,C$ and the erasure channel on $C$, the rotated Petz map is a recovery channel that acts on $B$ to recover the erased quantum information. The infidelity of the best recovery is upper bounded by the conditional mutual information (CMI). In this work, we study the infidelity of the rotated Petz map on several physically relevant long-range entangled quantum states. Specifically, we study three classes of quantum phases: (i) steady states of measurement-induced phase transitions, (ii) critical ground state under local measurements, and (iii) chiral states under local measurements. We find that the averaged infidelity of the Petz map recovery sharply distinguishes the three classes: (i) and (ii) are distinguished by the scaling of the infidelity with CMI and (iii) is characterized by an asymmetry of the fidelity with the rotation parameter. We also study Petz map recovery for topological order and find an operational interpretation of the topological entanglement entropy. Our result indicates that the recovery fidelity of the Petz map is a useful diagnostic of quantum phases of matter.

In principle, the probability of configurations, determined by the system's partition function or wave function, encapsulates essential information about phases and phase transitions. Despite the exponentially large configuration space, we show that the generic correlation of distances between configurations, with a degree of freedom proportional to the lattice size, can probe phase transitions using importance sampling procedures like Monte Carlo simulations. The distribution of sampled distances varies significantly across different phases, suggesting universal critical behavior for uncertainty and participation entropy. For various classical spin models with different phases and transitions, finite-size analysis based on these quantities accurately identifies phase transitions and critical points. Notably, in all cases, the critical exponent derived from the uncertainty of distances equals the anomalous dimension governing real-space correlation decay. Thus, configuration space correlations, defined by distance uncertainties, share the same decay ratio as real-space correlations, determining the universality class of phase transitions. This work applies to diverse lattice models with different local degrees of freedom, e.g., two levels for Ising-like models, discrete multilevels for $q$-state clock models, and continuous local levels for the $XY$ model, offering a robust, alternative method for understanding complex phases and transitions.