Achieving ultra-high-speed rotation of a nanomotor has significant implications for multiple disciplines and fields, such as small force sensing, quantum optics, and material testing. We developed an angular meta-accelerator to amplify the rotational dynamics of a nanomotor in vacuum, achieving the same GHz-level of rotational frequencies as in the literature, but under intensities that are two orders of magnitude lower. A straightforward and intuitive approach to achieving the rotation of a nanomotor involves transferring angular momentum to the nanomotor. However, the availability of incident angular momentum inevitably imposes an upper limit on the nanomotor's performance. Here, the angular meta-accelerator we propose, a structure with high rotational symmetry (composed of spheres or other shapes), effectively enhances the rotational speed of the nanomotor by up to 200 times compared to the situation without the meta-accelerator. The significant improvement in nanomotor performance originates from the meta-accelerator's selective focusing capability, which reconfigures external influences on the nanomotor. We analyze the enhancement of nanomotor performance in depth by decomposing the total field into different scattering channels as well as considering the spatial distribution of the scattering field. This approach of utilizing supplementary devices to enhance the performance of target devices not only provides valuable insights into overcoming inherent limitations but also unveils substantial potential for the design and development of advanced, complex mechanical systems in the future.

Initially unentangled states undergoing quantum chaotic dynamics are expected to evolve into featureless states at late times. While this expectation holds true on an averaged, coarse-grained level, it is unclear if this expectation applies to higher statistical moments, as symmetries present in physical systems constrain the exploration of Hilbert space. Here, we study the universal structure of late-time ensembles obtained from unitary dynamics in quantum chaotic systems with symmetries, such as charge or energy conservation. We find that while quantum states do not ergodically explore the entire Hilbert space at late times, the late-time ensemble typically becomes indistinguishable from Haar random states in the thermodynamic limit and at the level of finite statistical moments. Importantly, our results apply to initial states that are easy to prepare in ongoing experiments—specifically, product states—that lie in the middle of the spectrum of quantum chaotic systems. We show that typically these states not only exhibit the same late-time ensemble average as Haar random states, but also the same state-to-state fluctuations and higher statistical moments. In other words, there is no measurement—whether local or nonlocal—that one can perform at the level of finite statistical moments to tell that states are not exploring the entire Hilbert space. Interestingly, within the class of low-entanglement initial states, we also find atypical initial conditions in the middle of the spectrum of Hamiltonians known to be “maximally chaotic”. Such atypical initial states have smaller variance of the symmetry operator relative to that of Haar random states, and evolve into nonuniversal ensembles that can be distinguished from the Haar ensemble by simple measurements or subsystem properties. In the limiting case of initial states with negligible variance of the symmetry operator (e.g., states with fixed particle number or energy eigenstates), the late-time ensemble has universal behavior captured by constrained random state ensembles. On the one hand, our results reveal that an extremely high level of quantum state randomness can typically be achieved even when dynamics are constrained by symmetries; on the other hand, our results show that one can still achieve strongly nonergodic dynamics at “infinite temperature” within quantum chaotic regimes.

The characterization of quantum phase transitions is a fundamental task for the understanding of quantum phases of matter, with a number of potential applications in quantum technologies. In this work, we use digital quantum simulation as a resource to theoretically and experimentally study quantum phase transitions. More specifically, we implement the variational quantum eigensolver (VQE) algorithm for the one-dimensional spin-$1/2$ transverse-field Ising chain in the presence of boundary magnetic fields. Such fields can induce a rich phase diagram, including a first-order line and a continuous wetting transition, which is a quantum version of the classical wetting surface phenomenon. We present results for noiseless simulations of the associated quantum circuits as well as hardware results taken from a superconducting quantum processor. For different regions of the phase diagram, the quantum algorithm allows us to predict the critical value of the magnetic fields responsible for either the first- or second-order transitions occurring in the system.

Spin dynamics in the natural mineral aegirine, ${\mathrm{NaFeSi}}_2{\mathrm{O}}_6$, a member of the pyroxene family, was studied by elastic and inelastic neutron scattering. Magnetization and specific-heat measurements as well as single-crystal neutron diffraction maps, taken in the temperature range 2–20 K, confirm two successive magnetic transitions at 8.8 and 5.8 K, consistent with previous studies. The observed spin-wave excitations emerge from the incommensurate magnetic Bragg peaks corresponding to the propagation vector $k_{\mathrm{ICM}}=(0,0.77,0)$, and extend up to energies of about 1.5 meV. In the low-temperature helical phase, the spin dynamics of the ${\mathrm{Fe}}^{3+}$ ions is well described by a simple linear spin-wave model. The observed excitations can be modeled using a spin Hamiltonian that includes three primary exchange interactions—intrachain coupling $J=0.142\left(2\right)\mathrm{meV}$, and interchain couplings $J_1=0.083\left(1\right)\mathrm{meV}$ and $J_2=0.186\left(1\right)$ meV—and an easy-plane anisotropy $D=0.020\left(6\right)\mathrm{meV}$. Our results show that no single exchange interaction dominates the spin dynamics. The similar strengths of the intrachain and interchain couplings point to the fact that the magnetic interactions in aegirine are three dimensional rather than confined along one direction. As a result, the system cannot be considered quasi one dimensional, as previously suggested, and calls for further investigations.

We study the phonon behavior of the Co-based honeycomb frustrated magnet ${\mathrm{Na}}_2{\mathrm{Co}}_2{\mathrm{TeO}}_6$ under a magnetic field applied perpendicular to the honeycomb plane. The temperature and field dependence of the sound velocity and sound attenuation unveil prominent spin-lattice coupling in this material, promoting ultrasound as a sensitive probe for magnetic properties. An out-of-plane ferrimagnetic order is determined below the Néel temperature $T_N=27$ K. A comprehensive analysis of our data further supports a triple-$Q$ ground state of ${\mathrm{Na}}_2{\mathrm{Co}}_2{\mathrm{TeO}}_6$. Furthermore, the ultrasound data were systematically compared to the thermal transport results from literature, to unveil the importance of the phononic contribution to the observed transport behaviors.

Graphene nanoflakes (GNFs) exhibit rich magnetic behaviors arising from two primary mechanisms: geometry frustration in non-Kekulé structures and electron delocalization-driven aromatic stabilization in Kekulé-type systems. Herein, we develop a unified bonding entropy model (BEM) to quantitatively characterize the magnetic properties in GNFs within a statistical framework, providing an entropy-based criterion for understanding and predicting bond occupancy numbers and unpaired electron distributions. While non-Kekulé systems naturally favor high-spin configurations due to topological frustration, the BEM reveals that even Kekulé-type GNFs can exhibit magnetic character when the entropy gain from unpaired electrons outweighs the loss of aromatic stabilization. The model predictions show excellent agreement with density functional theory calculations in terms of spin density distributions and unpaired electron counts. Our results establish bonding entropy as a general guiding principle for designing carbon-based magnetic materials with tunable magnetic properties.

We study the interplay between on-site disorder and fermion pairing on the quasi-one-dimensional flat-band Creutz lattice. Both disorder and flat bands localize particles, but an attractive interaction results in pair formation and delocalization giving rise to superconductivity. In this work, we examine the attractive Hubbard model on the Creutz lattice to study the competition between these two effects and elucidate the properties of the superconducting phase and the localization quantum phase transition as the disorder strength is increased. Our main result is that flat-band superconductivity is robust against disorder: The critical disorder strength $W_c$ required to localize the fermion pairs and destroy superconductivity is finite at any interaction strength $U$ and is proportional to the superconducting weight $D_s$ of the clean system. Using large-scale density matrix renormalization group computations, we show that this transition is of the Berezinskii-Kosterlitz-Thouless form. In addition, even at very small interaction strength, the localization is not due to single-fermion localization but to pair localization. For completeness, we briefly study this disorder-induced localization with mean field theory and show that $W_c$ can be accurately determined by using an appropriate scaling function.

The emergence of a second superconducting dome through pressure-induced crystal structure manipulation has garnered considerable interest. Transition-metal chalcogenides (TMCs) offer a promising platform, as several binary compounds in this category have shown the second dome. Recently, ternary TMCs like $\mathrm{T}{\mathrm{a}}_2\mathrm{Pd}{\mathrm{S}}_6$ and $\mathrm{T}{\mathrm{a}}_2\mathrm{PdS}{\mathrm{e}}_6$ have also demonstrated pressure-driven superconductivity. In this study, we conducted electrical transport measurements on $\mathrm{T}{\mathrm{a}}_2\mathrm{Pd}{\mathrm{S}}_6$ and $\mathrm{T}{\mathrm{a}}_2\mathrm{PdS}{\mathrm{e}}_6$ at ultrahigh pressures exceeding 100 GPa, extending previous research into unexplored pressure regions to investigate the second dome. In both materials, the superconducting critical temperature ($T_{\mathrm{c}}$) initially decreases with increasing pressure, but above 100 GPa, $T_{\mathrm{c}}$ values significantly increase. Notably, $\mathrm{T}{\mathrm{a}}_2\mathrm{Pd}{\mathrm{S}}_6$ reaches a maximum $T_{\mathrm{c}}$ of 11.2 K at 130.0 GPa—a high record for ternary TMCs. The anomalous enhancements of $T_{\mathrm{c}}\mathrm{s}$ in $\mathrm{T}{\mathrm{a}}_2\mathrm{Pd}{\mathrm{S}}_6$ and $\mathrm{T}{\mathrm{a}}_2\mathrm{PdS}{\mathrm{e}}_6$ suggest the possible existence of the second dome, and further consideration is required, such as the application of hydrostatic pressure.

Intensive research has revealed intriguing optical responses in topological materials. This paper focuses on the optical responses in $s$-wave superconductors with Rashba spin-orbit coupling and a magnetic field, one of the platforms for topological superconductivity. On the one hand, to satisfy some conservation laws in superconducting responses, it is essential to take into account collective excitation modes. On the other hand, the optical response is a promising probe for detecting hidden collective modes in superconductors. In this paper, we investigate the effect of collective excitation modes on the linear and second-order optical responses based on the self-consistent response approximation, which is formulated using the Kadanoff-Baym method. The formulation takes into account the collective modes through the vertex corrections. Our main results reveal that the Higgs mode enhances the optical responses when the Fermi level is close to the Dirac point. The enhancement is because of the multiband effects characterized by interband pairing. We also demonstrate the sign reversal of the photocurrent conductivity around the topological transition with increasing Zeeman field. This finding supports the prediction in our previous work without considering collective excitation modes [Tanaka et al., Phys. Rev. B 110, 014520 (2024)]. The sign reversal phenomenon is attributed to the magnetic injection current modified by the Higgs mode, and is proposed as a bulk probe of topological superconductors. We also discuss the interplay of quantum geometry and collective modes.

The interplay of onsite quasiperiodic potential, superconductivity, and non-Hermiticity is explored in a non-Hermitian unconventional superconducting quasicrystal described by the Aubry-André-Harper model with $p$-wave pairing. Importantly, here the asymmetry is introduced in the hopping to break the reciprocity, leading to the explicit breaking of particle-hole symmetry. In the zero-pairing limit, the model hosts an exact triple-phase transition where the topological, metal-insulator, and real-to-complex spectral transitions coincide. With weak (perturbative) pairing, this coincidence survives only approximately and is progressively destroyed as the pairing strength increases. Additionally, instead of the Majorana zero modes (MZMs) found in the symmetric hopping case, we observe the emergence of in-gap states under open boundary conditions. These in-gap states are robust against disorder, underscoring their topological protection. Therefore, unlike the MZMs, which are very challenging to experimentally realize, these in-gap states can be used in topological quantum computational protocols.

Entanglement and stabilizer entropy are both involved in the onset of complex behavior in quantum many-body systems. Their interplay is at the root of complexity of simulability, scrambling, thermalization, and typicality. In this work, we study the dynamics of entanglement, stabilizer entropy, and the antiflatness of the entanglement spectrum after a quantum quench in a spin chain. We find that free-fermion theories show a gap in the long-time behavior of these resources compared to their random matrix theory value while nonintegrable models saturate it.

We investigate the entanglement of a ladder of spins formed by two sublattices, a “cluster” chain and the “environment”, consisting of independent spins, both coupled by an exchange interaction and evolving under a unitary discrete-time dynamics. The automaton is defined by the composition of the two-body spin-swap gate (between sublattices) and the three-body cluster interaction. We observe that, depending on the set of coupling constants, the cluster subsystem evolves towards states corresponding to different entanglement phases. In the weak-coupling regime the subsystem remains near the topological cluster state. Increasing the coupling strength leads to random states that transform from almost pure to fully mixed, according to the effective number of the environment's active degrees of freedom.

The Aharonov-Bohm (AB) caging is the phenomenon of extreme localization of particles subjected to magnetic fields in certain tight binding lattices. While the AB caging involves the localization of noninteracting particles, it often breaks down due to the effect of interaction, resulting in delocalization. In this study, however, we show that interactions under proper conditions can restore the AB caging of particles. By analyzing the dynamics of two bosons possessing both onsite and nearest neighbor interactions on a one-dimensional diamond/rhombus lattice pierced by an artificial gauge field, we show that the AB caging is restored when both interactions are of equal strength. Furthermore, the interaction induced AB caged bosons, with the onset of an antisymmetric correlated onsite disorder in the lattice, escape from the cages, demonstrating the phenomenon of inverse Anderson transition, which is known to be exhibited by the noninteracting AB caged particles. We also obtain a situation similar to the inverse Anderson transition when an external potential gradient is applied to the lattice. These findings offer a route to realize the AB caging and inverse Anderson transition of interacting particles in experiments involving ultracold atoms in optical lattices or superconducting circuits.

We study the dynamical structure factor of the frustrated spin-$3/2J_1\text{−}{J}_2$ Heisenberg chains, with particular focus on the partially dimerized phase that emerges between two Kosterlitz-Thouless transitions. Using a valence bond solid Ansatz corroborated by density-matrix renormalization-group simulations, we investigate the nature of magnon and spinon excitations through the single-mode approximation. We show that the magnon develops an incommensurate dispersion at $J_2\approx 0.32J_1$, while the spinons, viewed as domain walls between degenerate valence bond solid states, become incommensurate at $J_2\approx 0.4J_1$ beyond the Lifshitz point $(J_2\approx 0.388J_1)$. The dynamical structure factor exhibits rich spectral features shaped by the interplay between these excitations, with magnons appearing as resonances embedded in the spinon continuum. The spinon gap shows a nonmonotonic behavior, reaching a peak near the center of the partially dimerized phase and closing at the boundaries, suggesting the appearance of a floating phase as a result of the condensation of incommensurate spinons. Comparative analysis with the spin-$5/2$ case confirms the universality of these phenomena across half-integer higher-spin systems. Our results provide detailed insight into how fractionalization and incommensurate condensation govern the spectral properties of frustrated spin chains, offering a unified picture across different spin magnitudes.

We present a detailed investigation of an overlooked symmetry structure in noncollinear antiferromagnets that gives rise to an emergent quantum number for magnons. Focusing on the triangular-lattice Heisenberg antiferromagnet, we show that its spin-order parameter transforms under an enlarged symmetry group $\mathrm{SO}{\left(3\right)}_{\mathrm{L}}\times \mathrm{SO}{\left(2\right)}_{\mathrm{R}}$, rather than the conventional spin-rotation group $\mathrm{SO}\left(3\right)$. Although this larger symmetry is spontaneously broken by the ground state, a residual subgroup survives, leading to conserved Noether charges that, upon quantization, endow magnons with an additional quantum number, isospin, beyond their energy and momentum. Our results provide a comprehensive framework for understanding symmetry, degeneracy, and quantum numbers in noncollinear magnetic systems, and bridge an unexpected connection between the paradigms of symmetry breaking in noncollinear antiferromagnets and chiral symmetry breaking in particle physics.

We develop a real-space computational framework that integrates Chebyshev polynomial expansions with generalized Bogoliubov transformations to address anomalous quadratic interactions in magnon systems. The method enables efficient calculation of thermal transport coefficients through random trace evaluation and kernel damping techniques, significantly reducing computational costs compared to exact diagonalization methods. Applied to ${\mathrm{CrI}}_3$ ferromagnets, this approach reveals a temperature-driven sign reversal in thermal Hall effect that reflects the topology of magnon bands. The framework facilitates the implementation of real-space perturbations, for example, disorder, which slightly smears the sign-reversal behavior while markedly suppressing saturation magnitudes of thermal Hall conductivity. By incorporating thermal fluctuations near the Curie temperature, we can qualitatively reproduce experimental trends without introducing phenomenological parameters. The real-space implementation provides a universal platform for investigating topological thermal transport in magnetic systems with complex interactions.

We propose a superconducting ratchet-induced Hall effect (RHE), characterized by the emergence of a unidirectional, rectified flux of fluctuating Cooper pairs in a two-dimensional thin film exposed to an external electromagnetic field. The RHE is a second-order response with respect to the electromagnetic field amplitude. It consists of a nonzero photocurrent due to the breaking of the system's inversion symmetry driven by the combined action of the in-plane time-dependent electric field and a spatial modulation of the critical temperature. We explore a means to control the electric current by the polarization of the external field accompanied by a nonlinear Hall effect of fluctuating Cooper pairs caused by circularly polarized irradiation. Moreover, the nonlinear conductivity tensor exhibits a higher-power dependence on the reduced temperature compared to that of the conventional Aslamazov-Larkin correction (or other fluctuating second-order nonlinear responses). It results in a dramatic enhancement of the nonlinear Hall response of fluctuating Cooper pairs in the vicinity of the superconducting criticality.

Electronic density of states (DOS) plays a crucial role in determining and understanding materials properties. We investigate the machine learnability of additive atomic contributions to electronic DOS, focusing on atom-projected DOS rather than structural DOS. This approach for structure-property mapping is both scalable and transferable, and achieves high prediction accuracy for pure and compound silicon and carbon structures of various sizes and configurations. Furthermore, we demonstrate the generalizability of this model to complex Sn-S-Se compound structures. Utilizing locally trained DOS is shown to significantly enhance the accuracy of predicting material properties, including band energy, Fermi energy, heat capacity, and magnetic susceptibility. Our findings indicate that directly learning atomic DOS, rather than structural DOS, improves the efficiency, accuracy, and interpretability of machine learning in structure-property mapping. This streamlined approach reduces computational complexity, paving the way for examination of electronic structures in materials without the need for computationally expensive ab initio calculations.

We study the classification of two-dimensional (2D) topological orders enriched by point-group symmetries, by generalizing the folding approach, which was previously developed for mirror-symmetry-enriched topological orders. We fold the 2D plane hosting the topological order into the fundamental domain of the point group, which is a sector with an angle $2\pi /n$ for the cyclic point group $C_n$ and a sector with an angle $\pi /n$ for the dihedral point group $D_{2n}$, and the point-group symmetries become onsite unitary symmetries on the sector. The enrichment of the point-group symmetries is then fully encoded at the boundary of the sector and the apex of the section, which forms a junction between the two boundaries. The mirror-symmetry enrichment encoded on the boundaries is analyzed by the classification theory of symmetric gapped boundaries, and the point-group-symmetry enrichment encoded on the junction is analyzed by a framework for classifying symmetric gapped junctions between boundaries which we develop in this work. We show that at the junction, there are two potential obstructions, which we refer to as an $H^1$ obstruction and an $H^2$ obstruction, respectively. When the obstruction vanishes, the junction, and therefore the point-group-symmetry-enriched topological orders, are classified by an $H^0$ cohomology class and an $H^1$ cohomology class, which can be understood as an additional Abelian anyon and a symmetry charge attached to the rotation center, respectively. These results are consistent with the classification of onsite-symmetry-enriched topological orders, where the $H^1$ and $H^2$ obstructions and the junction correspond to the $H^3$ and $H^4$ obstructions for onsite symmetries, respectively.