We study the stability of localization under periodic driving in Stark many-body systems. We find that localization is stable except near special resonant frequencies, where resonances cause delocalization. We provide approximate analytical arguments and numerical evidence in support of these results. This shows that disorder-free broken ergodicity is stable to driving, opening up the way to studying nonequilibrium driven physics in a different setting.

While the zeros of complex partition functions, such as Lee-Yang zeros and Fisher zeros, have been pivotal in characterizing temperature-driven phase transitions, extending this concept to zero temperature remains an open question. In this work, we propose a solution to this issue by calculating the imaginary-temperature zeros (ITZs), which are defined as the roots of the imaginary-temperature partition function. We illustrate the analytical properties of ITZs in the transverse-field Ising chain, showing that the ITZs' distribution can distinguish between various phases and signify the critical exponents. Universal singular behaviors manifest in such quantities as the edge density of ITZs and the magnetization, with the scaling exponents remarkably differing from those in Lee-Yang theory. We further illuminate the consistency between ITZs and the zeros of the spectral form factor, which offers a practical path for the experimental detection of ITZs.

Materials that exhibit obvious low-dimensional quantum magnetism but ultimately still undergo long-range magnetic ordering are very interesting. Herein, we report a material of this kind—$S=1$ screw chain single crystal ${\mathrm{CaNi}}_2{\mathrm{Te}}_3{\mathrm{O}}_8{\mathrm{Cl}}_2$. The compound crystalizes in monoclinic structure (space group $P{2}_1/n$). The magnetic susceptibility along the easy axes exhibits a broad maximum at $T_{\text{max}}=11.41\left(5\right)\mathrm{K}$ ($a$* axis) and 11.27(5) K ($b$ axis) followed by a long-range antiferromagnetic order at $T_{\text{N}}=9.08\left(5\right)\mathrm{K}$ ($a$* axis) and 8.78(5) K ($b$ axis), pointing to a transition from one-dimensional (1D) quantum disorder to three-dimensional classical order. The magnetization presents a spin-flop transition, proving that single-ion anisotropy is small compared to exchange interaction. The specific heat data demonstrate the presence of 1D disorder or short-range magnetic correlations persisting up to 3 $T_{\text{N}}$. The density functional theory calculations yield two intrachain exchanges ($-7.89\mathrm{K}$ and $-6.95\mathrm{K}$) and an average interchain coupling ($-3.56\mathrm{K}$). The latter are mediated through the Te ion and responsible for the occurrence of antiferromagnetic order. With the available experimental data, temperature-field phase diagrams are constructed, implying the presence of a field-induced order-to-disorder transition. The title compound is a rare screw chain antiferromagnet indicating coupled bond-alternating chain features.

Transport plays a key role in characterizing topological insulators and semimetals. Understanding the effect of disorder is crucial to assess the robustness of experimental signatures for topology. In this work, we find the absence of localization in nodal-line semimetals for long-range scalar disorder and a large range of disorder strengths. Using a continuum transfer matrix approach, we find that the conductivity in the plane and out of the plane of the nodal line increases with system size and disorder strength. We substantiate these findings with a perturbative calculation and show that the conductivity increases with disorder strength using the Kubo formula in the self-consistent Born approximation. We also find that the system remains metallic for vector disorder and that vector disorder can drive a transition from an insulating to a metallic regime. Our results demonstrate the absence of localization in a three-dimensional bulk system.

We predict intrinsic spin relaxation times $\left(T_1\right)$ of graphite due to spin-orbit–phonon interaction, i.e., spin-phonon interaction caused by spin-orbit coupling and electron-phonon interaction, using our developed first-principles density-matrix approach. We obtain ultralong $T_1$, e.g., $\approx 600\mathrm{ns}$ at 300 K, which leads to ultralong in-plane spin diffusion length $\approx 110\mu \mathrm{m}$ within the drift-diffusion model. Our prediction sets the upper bound of $T_1$ of graphite at each given temperature and Fermi level. The anisotropy ratios of $T_1$ or values of $T_{1z}/T_{1x}$ are found small and around 0.6. We examine the applicability of the well-known Elliot-Yafet (EY) relation, which declares that spin relaxation rate $T_{1\alpha }^{-1}$ $(\alpha =x,y,z)$ is proportional to the product of the ensemble average of spin mixing parameter $\langle b_{\alpha }^2\rangle$ and carrier relaxation rate ${\tau }_p^{-1}$. Our numerical tests suggest that the EY relation works qualitatively if the degeneracy threshold $t^{\mathrm{deg}}$ for evaluating $b_{\alpha }^2$ is relatively large (not much smaller than or comparable to $k_{B}T$), e.g., ${10}^{-3}\mathrm{eV}$ or larger, but fails if $t^{\mathrm{deg}}$ is too tiny (much smaller than $k_{B}T$), e.g., ${10}^{-6}\mathrm{eV}$ or smaller.

We extend previous inelastic neutron scattering results on the geometrically frustrated antiferromagnet hexagonal-${\mathrm{YMnO}}_3$, which has been suggested to belong to the class of classical spin liquids. We expand the energy transfer range of the diffuse signal up to 6.9 meV within a wide temperature range around the ordering temperature, $T_{\mathrm{N}}$. The two distinct diffuse signals in the $a\text{−}b$ plane, the signal localized at ${\mathrm{\Gamma }}^{\prime }$ and the scattering intensity connecting ${\mathrm{\Gamma }}^{\prime }$ points over the ${\mathrm{M}}^{\prime }$, are shown to be only weakly energy dependent. In addition, an external magnetic field of up to 10.5 T applied along $c$ is shown to have no effect on the diffuse signal. In the orthogonal scattering plane, the signals are shown to be dependent on $l$ only through the magnetic form factor, showing that the correlations are purely two-dimensional, and supporting the origin of this to be the frustrated ${\mathrm{Mn}}^{3+}$ triangles. This result is corroborated by atomistic spin dynamics simulations showing similar scattering vector and temperature behaviors. Lastly, data for the spin wave scattering in the $(h,0,l)$ plane allow for a discussion of the magnetic ground state where better agreement is found between the data and an ordered structure of the ${\mathrm{\Gamma }}_1$ or ${\mathrm{\Gamma }}_3$ symmetry, albeit crystal electric field arguments dismiss the ${\mathrm{\Gamma }}_1$ as a possibility.

Finite depth quantum circuits provide an equivalence relation between gapped phases. Moreover, there can be nontrivial domain walls either within the same gapped phase or between different gapped phases, whose equivalence relations are given by finite depth quantum circuits in one lower dimension. In this paper, we use such unitary equivalence relations to study the fusion of one-dimensional gapped phases. In particular, we use finite depth circuits to fuse two gapped phases, local unitaries to fuse two domain walls, and a combination of both to fuse gapped phases with domain walls. This provides a concrete illustration of some simple aspects of the higher-category structure of gapped defects in a higher-dimensional trivial gapped bulk state.

The interacting SSH model provides an ideal ground to study the interplay between topologically insulating phases and electron-electron interactions. We study the polarization density as a topological invariant and provide an analytic treatment of its behavior in the low-energy sector of the one-dimensional interacting SSH model. By formulating the topological invariant in terms of Green's functions, we use the low-energy field theory of the Thirring model to derive the behavior of the polarization density. We show that polarization density in the continuum theory describes the usual topological insulating phases. Still, it contains an extra factor from the fields' scaling dimensions in the low-energy quantum field theory. We interpret this as a measure of the modified charge of the new excitations in the system. We find two distinct contributions: a renormalization of the electronic charge $e$ of a Fermi liquid because of quasiparticle smearing and an additional contribution coming from the topological charge of the soliton arising in the bosonized version of the Thirring model, the sine-Gordon model.

Many-body correlations are known to be responsible for a broad range of fascinating physical phenomena, introducing corrections that appear elusive at the single-particle level. An example of this is the Lifshitz transition that occurs as the Fermi surface topology changes when, e.g., Coulomb interaction effects break into the picture. The Fermi velocity renormalization can lead a type-II Weyl semimetal at mean-field level to become a trivial or a type-I Dirac material when correlations are accounted for, which is far from being obvious. In this paper, we scrutinize the band structure of ${\mathrm{NiTe}}_2$, a material that features a type-II Dirac point (DP) near the Fermi level, within the mean-field approach. Including GW-level correlations, our findings showcase anisotropic corrections on the Dirac carrier velocity exceeding $100\%$ enhancements, underscoring the nuanced influence of electronic interactions in the band structure. We also consider type-II Dirac crossings in ${\mathrm{PtSe}}_2$ and ${\mathrm{PtTe}}_2$ and observe that, including many-body effects via GW, the band topology changes, featuring trivial topology and type-I Dirac crossings, respectively. Our findings highlight the necessity to evaluate the many-body effects on nontrivial bands, contributing essential insights into the broader exploration of many-body correlation effects in type-II DPs of condensed-matter systems.

Controllable magnetization in atomically thin two-dimensional magnets is highly desirable for developing spintronics. For FeSe monolayer, its magnetic ground state is not yet fully understood, and the potential in constructing high-speed and advanced devices remains unknown. Using density functional theory calculations, we confirm the spin ordering of monolayer FeSe to be dimer texture. With fluorine (F) adsorption (F/FeSe), the system exhibits a coverage dependent magnetic anisotropy and multiferroicity which can be attributable to the Jahn-Teller effect, being a possible benefit to potential spintronic applications. Intriguingly, an inherent coupling between magnetism and ferroelasticity in the most energetically favorable F/FeSe system is proposed. Our study thus not only provides a promising way to control the spintronic properties and construct multiferroics, but also renders F/FeSe an ideal platform for magnetism studies and practical high-performance multifunctional devices.

Conducting altermagnets have recently emerged as intriguing materials supporting strongly spin-polarized currents without magnetic stray fields. We demonstrate that altermagnets enable three key functionalities, merging superconductivity and spintronics. The first prediction is a controllable supercurrent-induced edge magnetization, which acts like a dissipationless spin-splitter effect. The second and third predictions are a Cooper pair spin-splitter and a filtering effect, respectively. These effects allow for spatial separation of triplet pairs with opposite spin polarizations and spin-selective tunneling of Cooper pairs. We derive a quasiclassical theory with associated boundary conditions that describe these phenomena and explain how they can be experimentally verified. Our results open a new path for spatial control of spin signals via triplet Cooper pairs using hybrid superconductor-altermagnet devices.

FeSe films are of great interest owing to their rich physical properties and good application prospects. Here, we successfully grew a 40-unit-cell-thick high-$T_{\mathrm{c}}$ FeSe/STO films (onset superconducting transition temperature $T_{\mathrm{c}}^{\mathrm{onset}}\sim 28.3\mathrm{K},$ zero-resistance transition temperature $T_{c0}\sim 23\mathrm{K}$) using a custom-designed pulsed laser deposition–scanning tunneling microscopy (PLD-STM) system. Using in situ STM, large-area terraced surfaces and high atomic resolution of FeSe thin films were observed, marking layered FeSe growth via PLD. Hall and magnetoresistance measurements showed minimal changes in carrier concentration compared to $\mathrm{FeSe}/\mathrm{Ca}{\mathrm{F}}_2$ films with $T_{\mathrm{c}}$ of 8 K, and the Berezinskii-Kosterlitz-Thouless transition analysis indicated the presence of the two-dimensional nature of superconductivity. By angle-resolved photoemission spectroscopy experiment, a band with a large effective electron mass was discovered, which is similar to other high-$T_{\mathrm{c}}$ FeSe systems obtained through alkali-metal doping, etc, suggesting that enhanced electron correlations are crucial for the $T_{\mathrm{c}}$ increase in this system. This work provides guidance for the growth of high-quality superconducting thin films, and provides valuable insight into the mechanisms driving superconductivity in FeSe-based systems.

${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ has garnered widespread interest recently due to its high-temperature superconductivity under pressure, accompanied by charge density wave (CDW) ordering and metal-insulator (MI) transitions in the phase diagram. Here, we explore the nature of CDW and MI transitions using comprehensive first-principles calculations. Our findings reveal that ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ possesses an antiferromagnetic ground state under both low and high pressures, with the strong Fermi surface nesting contributed by the flat band that leads to phonon softening and electronic instabilities. Accordingly, several stable CDW orders with oxygen octahedral distortions are identified. In the presence of apical oxygen vacancies, we identify two different phases exhibiting distortions similar to CDW phases, and their competition can lead to a pressure-induced MI transition. The estimated CDW transition temperature and MI transition pressure agree nicely with experiments. In addition, we find that the electron-phonon coupling is too weak to contribute to superconductivity. These results suggest an unconventional superconducting pairing mechanism mediated by antiferromagnetic fluctuations. Finally, we present a phase diagram consistent with the experimental results. Our findings offer crucial insights into the interplay of superconductivity, CDW, and the role of oxygen vacancies in pressurized ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$.

Topological insulators show important properties, such as topological phase transitions and topological edge states. Although these properties and phenomena can be simulated by well-designed circuits, it remains a complex task to design such topological circuits due to the intricate physical principles and calculations involved. Therefore, achieving a framework that can automatically complete bidirectional design of topological circuits is very significant. Here, we propose an effective bidirectional collaborative design framework with strong task adaptability, which can automatically perceive inputs and generate outputs in arbitrary combinations of text and images. In the framework, a large language model (LLM) is connected to multimodal and different encoders, which involves building a shared multimodal space by bridging alignment in the diffusion process. For simplicity, a series of two-dimensional Su-Schrieffer-Heeger circuits is constructed with different structural parameters. The framework at first is applied to find the relationship between the structural information and topological features. Then the correctness of the results through experimental measurements can be verified by the automatically generated circuit diagram following the manufacture of a printed circuit board. The framework achieves good results in the reverse design of circuit structures and forward prediction of topological edge states, reaching an accuracy of 94%. The key feature of our framework is its ability to effectively learn the bidirectional mapping between circuit structure and topological impedance response across the spectrum. While recently LLMs have made exciting strides, as humans always communicate through various modalities, developing a framework capable of accepting and delivering content in more modalities becomes essential to human-level artificial intelligence. Overall, in this paper, we demonstrate the enormous potential of the proposed bidirectional deep learning framework in complex tasks and provide insights for collaborative design tasks.

The ${}^{1}E$–${}^{1}A_1$ singlet manifold of the negatively charged nitrogen vacancy ($\mathrm{N}{V}^{-}$) center in diamond plays a central role in its quantum-information and quantum-sensing applications. However, the energy gap between the ${}^{1}E$ singlet state and diamond band edges or the ${}^{3}A_2$–${}^{3}E$ triplet manifold has not been measured directly. Using the magnetic-field quenching effect on the $\mathrm{N}{V}^{-}$ photoluminescence (PL) spectra, we measure these energy gaps as a function of temperature, applied magnetic field, excitation wavelength, and excitation power in a heavily nitrogen-doped sample. Increased PL and decreased zero-phonon line width from the $\mathrm{N}{V}^0$ center were observed in the presence of an applied magnetic field, indicating ionization from the long-lived ${}^{1}E$ singlet state. A temperature-dependent ionization threshold between 532 and 550 nm was found, locating the singlet states within the diamond band gap.