Thouless charge pumping or transport of quantum mechanical particles through a periodic modulation of the system Hamiltonian exhibiting a topological phase transition is known to be unstable in the presence of strong disorder in the system. In this paper, however, we show that in a one-dimensional Su-Schrieffer-Heeger lattice, an onsite quasiperiodic disorder favors a quantized particle transport and hence a robust Thouless charge pumping. This unusual property is found to be due to an emergence of a topological to trivial phase transition as the quasiperiodic disorder strength is increased. This transition allows us to propose a nonstandard pumping scheme where a periodic modulation of the disorder strength also favors a quantized Thouless charge pump. Our model and prediction may be simulated in state-of-the-art ultracold atomic setups.

Magnetic anisotropy is one of the important factors in determining magnetic structures. The type of magnetic anisotropy is closely related to the symmetry of crystals. We theoretically investigate magnetic anisotropy and its related magnetic instability arising from an electric axial moment, which appears under the breaking of the mirror symmetry parallel to the moment but does not require the breakings of both spatial inversion and time-reversal symmetries. By performing perturbation and mean-field calculations in a complementary way, we show the appearance of the in-plane magnetic anisotropy when the electric axial moment occurs, which tends to tilt in-plane spin moments from the crystal axes in collaboration with relativistic spin-orbit coupling. We demonstrate such a tendency for single-sublattice and four-site cluster models. In the four-site cluster model, we show that a spin configuration consisting of magnetic monopole and magnetic toroidal dipole tends to be realized in the region where a spin vortex is stabilized by the exchange interactions.

We present a combined neutron diffraction and high-field muon spin rotation ($\mu \mathrm{SR}$) study of the magnetically ordered and superconducting phases of the high-temperature superconductor ${\mathrm{La}}_{1.94}{\mathrm{Sr}}_{0.06}{\mathrm{CuO}}_{4+y} [T_{\mathrm{c}}=37.5\left(2\right)$ K] in a magnetic field applied perpendicular to the ${\mathrm{CuO}}_2$ planes. We observe a linear field-dependence of the intensity of the neutron diffraction peak that reflects the modulated antiferromagnetic stripe order. The magnetic volume fraction extracted from $\mu \mathrm{SR}$ data likewise increases linearly with applied magnetic field. The combination of these two observations allows us to unambiguously conclude that stripe-ordered regions grow in an applied field, whereas the stripe-ordered magnetic moment itself is field-independent. This contrasts with earlier suggestions that the field-induced neutron diffraction intensity in La-based cuprates is due to an increase in the ordered moment. We discuss a microscopic picture that is capable of reconciling these conflicting viewpoints.

In this work, we discuss properties with no static counterpart arising in Floquet topological insulators with a dynamical chiral symmetry (DCS), i.e., a chiral symmetry which is present while driving. We explore the topological properties of Floquet insulators possessing a DCS which either does or does not survive upon taking the static limit. We consider the case of harmonic drives and employ a general framework using the quasienergy operator in frequency space. We find that for a DCS with no static analog, the presence of driving has a negligible impact on the topological phases associated with zero quasienergy. In stark contrast, topological gaps can open at $\pi$ quasienergy and mainly occur at momenta where the driving perturbation vanishes. We confirm the above general predictions for an extended Kitaev chain model in the BDI symmetry class. Another possibility that opens up when adding the drive, while preserving chiral symmetry, is symmetry-class conversion. We demonstrate such an effect for a static CI class Hamiltonian which is topologically trivial in one dimension. By considering a suitable driving, we obtain a $\mathrm{CI}\to \mathrm{AIII}$ transition, which now enables the system to harbor topological $\pi$ modes. Notably, the arising topological phases strongly depend on whether or not the DCS has a static analog. Our results bring Floquet insulators with nonstandard DCS forward as ideal candidate platforms for engineering and manipulating topological $\pi$ modes.

Inertial effects in spin dynamics emerge on picosecond timescales, giving rise to nutational excitations at THz frequencies. Here, we describe a general framework for investigating the precessional and nutational excitations in any type of spin structure within linear spin-wave theory. We consider the particular cases of planar and conical spin spirals in detail. We observe a change in the sign of the curvature of the high-frequency nutational spin-wave band as the spiral period is decreased when passing from the ferromagnetic to the antiferromagnetic limit. We identify conditions for the interaction parameters where the curvature changes sign and asymptotical flat bands are formed.

The dynamical magnetic properties of the icosahedral $i\text{−}\mathrm{Tb}\text{−}\mathrm{Cd}$ quasicrystal (QC) were investigated by means of squid magnetometry. At low temperatures, below $\mathrm{T}\sim 4.5 \mathrm{K}$, we observe conventional spin glass features including aging, memory, and rejuvenation. Interestingly, from $\mathrm{T}\sim 4.5$ to 10 K, the spin configuration is also found to evolve with time (i.e., age as in spin glass), yet without memory. This suggests a reentrantlike behavior for the $i\text{−}\mathrm{Tb}\text{−}\mathrm{Cd} \mathrm{QC}$, where upon cooling from high temperatures, the system first displays a magnetically frustrated phase before turning into a spin glasslike one at the lowest temperatures. We discuss the nature and possible origin of this magnetic behavior, in the light of the results obtained in the $i\text{−}\mathrm{Gd}\text{−}\mathrm{Cd} \mathrm{QC}$, and ternary Tb-based quasicrystal approximants.

The interplay of non-Hermitian (NH) spin dynamics in coupled ferromagnetic (FM) systems has unveiled intriguing phenomena, notably the manifestation of FM-antiferromagnetic (AFM) phase transitions at exceptional points (EPs). Extending beyond traditional FM media, ferrimagnetic (FiM) media combine the advantages of AFM and FM systems, displaying distinct attributes especially at the angular momentum composition (AMC) point, $x_{\mathrm{AMC}}$. This study explores the profound influence of FiM composition on the NH spin dynamics of a coupled FiM system. At $x_{\mathrm{AMC}}$, the spin dynamics depicted by the Néel vector demonstrates a parity-time $\left(\mathcal{PT}\right)$ symmetry, exhibiting power-law frequency splitting concerning external perturbations at the EP with a fixed power of 1/2. However, deviation from $x_{\mathrm{AMC}}$ leads to partial converging of eigenfrequency branches at the EP owing to the uncompensated angular momentum, displaying power-law frequency splitting with varied powers, akin to an effective coupled RLC circuit with capacitance influenced by frequency variations. This investigation opens a unique avenue in the area of $\mathcal{PT}$ symmetry in magnetic NH systems, unraveling the nuanced behaviors of coupled FiM configurations.

This theoretical study unveils the potential for ultrafast skyrmion generation in magnetic thin films, driven by the remarkable plasmonic properties of gold nanoparticles. By combining the plasmonic, photothermal, and micromagnetic analysis, we explore size-dependent light absorption, resonance wavelength, and electric field distribution around the nanoparticles. Our findings highlight the crucial role of the insulating layer's thickness in enhancing plasmonic effects, offering tunable absorption characteristics. Micromagnetic calculations demonstrate the efficient creation of Néel skyrmions in the range of a few tens of ps, showcasing a breakthrough in magnetic phenomena and opening thus a path for functional skyrmionic-based devices.

The magnetic order in ${\mathrm{BaFe}}_2{\mathrm{Se}}_3$, an iron-based spin ladder that is superconducting under pressure, is intensely studied due to the intimate relation between magnetism and superconductivity. In the present paper, we have performed a comprehensive study of structural, magnetic, and electronic properties on $\mathrm{Ba}{\left({\mathrm{Fe}}_{1-x}{\mathrm{Ni}}_x\right)}_2{\mathrm{Se}}_3$ ($0\le x\le 0.2)$ and ${\mathrm{BaFe}}_2{\left({\mathrm{Se}}_{1-y}{\mathrm{Te}}_y\right)}_3$ $(0\le y\le 0.15)$. Neutron powder diffraction measurements were performed on the Ni-doped sample up to $x=0.1$ and ${\mathrm{BaFe}}_2{\left({\mathrm{Se}}_{0.85}{\mathrm{Te}}_{0.15}\right)}_3$. Our results show that the block magnetic order remains as the ground state for $x\le 0.05$ in $\mathrm{Ba}{\left({\mathrm{Fe}}_{1-x}{\mathrm{Ni}}_x\right)}_2{\mathrm{Se}}_3$. Additionally, for ${\mathrm{BaFe}}_2{\left({\mathrm{Se}}_{0.85}{\mathrm{Te}}_{0.15}\right)}_3$, the block magnetic structure is even more robust. As for the resistivity, it decreases with increasing Ni content while it barely changes with Te doping. The observed negligible change of the magnetic propagation wave vector as a function of Ni content seems to contradict the orbital selective Mott Phase proposed previously.

Magnetic topological semimetals LnSbTe ($Ln=\mathrm{lanthanide}$) have attracted intensive attention because of the presence of interplay between magnetism, topological, and electron correlations depending on the choices of magnetic Ln elements. Recently, varying Sb-Te composition has been found to effectively control the electronic and magnetic states in $Ln\mathrm{S}{\mathrm{b}}_x\mathrm{T}{\mathrm{e}}_{2-x}$. With this motivation, we report the evolution of magnetic properties with Sb-Te substitution in $\mathrm{NdS}{\mathrm{b}}_x\mathrm{T}{\mathrm{e}}_{2-x+\delta }$, $(0\le x\le 1)$. Our work reveals the interesting nonmonotonic change in magnetic ordering temperature with varying composition stoichiometry. In addition, reducing the Sb content $x$ drives the reorientation of moments from in-plane ($ab$-plane) to out-of-plane ($c$-axis) direction that results in the distinct magnetic structures for two end compounds $\mathrm{NdT}{\mathrm{e}}_2$ $\left(x=0\right)$ and NdSbTe $\left(x=1\right)$. Furthermore, the moment orientation in $\mathrm{NdS}{\mathrm{b}}_x\mathrm{T}{\mathrm{e}}_{2-x+\delta }$ is also found to be strongly tunable upon application of a weak magnetic field, leading to rich magnetic phases depending on the composition stoichiometry, temperature, and magnetic field. Such strong tuning of magnetism in this material establishes it as a promising platform for investigating tunable topological states and correlated topological physics.

We theoretically study first- and second-order optical responses in a transition-metal dichalcogenide monolayer with distinct trivial, nodal, and time-reversal invariant topological superconducting (TRITOPS) phases. We show that the second-order dc response, also known as the photogalvanic response, contains signatures for differentiating these phases while the first-order optical response does not. We find that the high-frequency photogalvanic response is insensitive to the phase of the system, while the low-frequency response exhibits features distinguishing the three phases. At zero doping, corresponding to an electron filling in which the Fermi level lies at nodal points, there are opposite sign zero-frequency divergences in the response when approaching the nodal phase boundaries from the trivial and the TRITOPS phases. In the trivial phase, both the high-frequency and low-frequency response of the system are negative, but in the TRITOPS phase the low-frequency response becomes positive while the high-frequency response remains negative. Furthermore, since phase transitions are controlled by the Rashba spin-orbit coupling and the ratio of intraorbital and interorbital paring amplitudes, our results not only help distinguish the phases but they can also provide an estimate of the pairing amplitudes based on the photogalvanic response of the system.

For the Fermi-Hubbard model in the strongly interacting Mott insulator state, we study the prethermalization dynamics after a quench (switching on the hopping rate). To this end, we employ the method of the hierarchy of correlations and compare different levels of accuracy. To leading order, the usual free quasiparticle dynamics (as encoded in the two-point correlation functions) yields the standard picture of prethermalization. Taking into account the back-reaction of these quasiparticle fluctuations onto the mean-field background as the first next-to-leading-order effect, we observe a strong degradation of prethermalization, especially in low dimensions. In contrast, the inclusion of three-point correlations enhances prethermalization.

Signatures of photoinduced superconductivity have been reported in cuprate materials subjected to a coherent phonon drive. A “cold” superfluid was extracted from the transient Terahertz conductivity and was seen to coexist with “hot” uncondensed quasiparticles, a hallmark of a driven-dissipative system of which the interplay between coherent and incoherent responses is not well understood. Here, time resolved spontaneous Raman scattering was used to probe the lattice temperature in the photoinduced superconducting state of ${\mathrm{YBa}}_2{\mathrm{C}\mathrm{u}}_3{\mathrm{O}}_{6.48}$. An increase in lattice temperature of up to 140 K was observed by measuring the time dependent Raman scattering intensity of an undriven “spectator” phonon mode. This value is consistent with the estimated increase in quasiparticle temperature measured under the same excitation conditions. These temperature changes provide quantitative information on the nature of the driven state and its decay, and may suggest a strategy to optimize this effect.

The effects of a magnetic field on the Mott transition, a longstanding issue in condensed matter physics, are studied using magnetoresistance measurements for organic Mott insulators, $\lambda \text{−}{\left(\text{BETS}\right)}_2{\mathrm{GaBr}}_x{\mathrm{Cl}}_{4-x}$, up to 55 T. We demonstrate that an insulator-to-metal transition with a first-order nature and a successive superconductor-to-insulator-to-metal transition are induced by magnetic fields. We discuss the difference in magnetic susceptibility between the insulating and metallic phases, which is a key factor in inducing these transitions. Field induced transitions in experimentally feasible fields under ambient pressure conditions lead to further experimental verification of Mott transitions.

We study transport through interfaces in topological nodal-line semimetal (NLS), focusing on two geometries: a single interface between two large samples, one NLS and one metal, and an infinite NLS slab in between two metallic regions. We investigate the dependence of the spectra on the boundary conditions, showing how they affect the surface states and the band dispersion. We find a set of drum states, arising from the hybridization of the drumhead states on opposite surfaces at finite slab width, and describe their signatures in the transport properties of a clean sample. Finally, we compute the electronic trajectories in the ballistic regime and show that there is a series of resonant angles that ensure perfect transmission. We also show how the current density profile acquires an inhomogeneous distribution in the radial direction.

As one class of typical quantum materials, kagome metals in $A{\mathrm{V}}_3{\mathrm{Sb}}_5(A=\mathrm{K},\mathrm{Rb},\mathrm{Cs})$ have attracted extensive attention due to their interesting physical properties and different quantum phases of charge-density wave (CDW), superconductivity, and nontrivial topology. Recently, a new CDW phase in ${\mathrm{ScV}}_6{\mathrm{Sn}}_6$ was experimentally observed and inspired a wide study of the mechanism of driving force. To have a clear understanding of the correlation effect in the CDW phase in ${\mathrm{ScV}}_6{\mathrm{Sn}}_6$, we performed a systematic density functional theory plus dynamical mean-field theory ($\mathrm{DFT}+\mathrm{DMFT}$) calculations. The resulting static local spin susceptibility is nearly independent of temperature, indicating the absence of local moment on atom V, in full agreement with experimental measurements. The mass enhancements of quasiparticles and bandwidth renormalizations near the Fermi level show a weak correlation strength in ${\mathrm{ScV}}_6{\mathrm{Sn}}_6$. In addition, the comparable mass enhancements of quasiparticles in ${\mathrm{ScV}}_6{\mathrm{Sn}}_6$ with CDW order and ${\mathrm{YV}}_6{\mathrm{Sn}}_6$ without CDW phase suggests that electronic correlations corresponding to Fermi-surface nesting do not play the dominant role in the formation of CDW order in ${\mathrm{ScV}}_6{\mathrm{Sn}}_6$.

We use stochastic series expansion (SSE) quantum Monte Carlo (QMC) methods to study the phases and transitions displayed by a class of sign-free designer Hamiltonians for $\mathrm{SU}\left(N\right)$ analogs of spin $S=1$ quantum antiferromagnets on the square lattice. The $\mathrm{SU}\left(N\right)$ spins are generators of the single-row two-column representation (complex conjugate of single-row two-column representation) on $A$ ($B$) sublattices of the square lattice, and the Hamiltonian is designed to explore the competition between the nearest-neighbor antiferromagnetic exchange couplings $J$ and four-spin interactions $Q$ that favor a plaquette-ordered valence bond solid (p-VBS) ground state. We find that this state is indeed established at large $Q/J$ for all $N>3$. For $3<N\le 9$, the ground state exhibits a direct first-order quantum phase transition from a small-$Q/J$ Néel ordered antiferromagnetic state to this large-$Q/J$ p-VBS state. The ground state at $Q/J=0$ for $N\ge 10$ has been previously reported to be a valence bond nematic state, dubbed the Haldane nematic in recent literature. For small nonzero $Q/J$ and $N\ge 10$, we additionally find an unusual intermediate state in which the four-site plaquette energy has a Bragg peak at wave vector $(\pi ,\pi )$ with no accompanying Bragg peaks at wave vectors $(\pi ,0)$ and $(0,\pi )$. This $(\pi ,\pi )$ state also appears to be metastable at $Q/J=0$, as evidenced by low-temperature histograms of the Haldane nematic and $(\pi ,\pi )$ order parameters. Deep in the p-VBS phase of the ground state phase diagram, we find the temperature-driven melting of the p-VBS order is in the Ashkin-Teller universality class. In this regime, we identify an interesting signature of Ashkin-Teller criticality in four-site plaquette singlet correlations at wave vector $(\pi ,\pi )$; this is in addition to the expected critical fluctuations of the conventional p-VBS order parameter at wave vectors $(\pi ,0)$ and $(0,\pi )$.

For the photocatalytic water splitting, the oxygen evolution reaction on transition-metal oxide photoanodes is well known to be the bottleneck. As strongly correlated materials, strong electron-phonon couplings in transition-metal oxides indicate that atomic vibrations can greatly modify electronic structure and transport properties. By combining density functional theory and molecular dynamics, we study the effects of finite-temperature atomic vibrations on the band gaps, electronic localization, polaron formation, absorption spectra, and the band-edge levels in $\alpha \text{−}{\mathrm{Fe}}_2{\mathrm{O}}_3$. Atomic vibrations are found to induce strong electronic localization near the band edges and facilitate the hole polaron formation, which can hinder the transport of the photogenerated holes. In addition, atomic vibrations push up the valence band edge, indicating an increased reaction barrier. This study identifies that atomic vibrations in transition-metal oxide photoanodes can limit the efficiency of the oxygen evolution reaction.