${\mathrm{CeTa}}_7{\mathrm{O}}_{19}$ is a recently found two-dimensional triangular lattice antiferromagnet without showing magnetic order. We grew high-quality ${\mathrm{CeTa}}_7{\mathrm{O}}_{19}$ single crystals and studied the low-temperature magnetic susceptibility, specific heat, and thermal conductivity. The dc magnetic susceptibility and magnetization reveal its nature of effective spin-1/2, easy axis anisotropy, and antiferromagnetic spin coupling. The ultralow-temperature ac susceptibility and specific heat data indicate the absence of any phase transition down to 20 mK. The ultralow-temperature thermal conductivity $\left(\kappa \right)$ at zero magnetic field exhibits a nonzero residual term ${\kappa }_0/T=0.0056$ $\mathrm{W}/{\mathrm{K}}^2\mathrm{m}$. Although the magnetic field dependence of $\kappa$ is rather weak, the 14 T thermal conductivity shows an essential zero residual term. All these results point to a possible ground state of quantum spin liquid.

The metal-insulator transition of overdoped infinite-layer nickelates at low temperature has not been clearly explained. In this study, magnetoresistance and the corresponding conductance correction of the overdoped infinite-layer $\mathrm{L}{\mathrm{a}}_{1-x}\mathrm{S}{\mathrm{r}}_x\mathrm{Ni}{\mathrm{O}}_2$ films were fitted by the Kondo model and the Hikami-Larkin-Nagaoka formula, respectively. Moreover, the temperature dependence of resistivity is well modeled using contributions mainly from Kondo scattering and weak localization (WL). The results show that the metal-insulator transition of the overdoped infinite-layer $\mathrm{L}{\mathrm{a}}_{1-x}\mathrm{S}{\mathrm{r}}_x\mathrm{Ni}{\mathrm{O}}_2$ films at low temperature is mainly due to the combined effect of Kondo scattering and WL. With the increase of Sr doping concentration, the contribution from the Kondo scattering gradually weakens and WL becomes dominant, which is consistent with the predictions of the self-doped Mott-Kondo theory. Our work contributes to elucidating the physical properties of overdoped $\mathrm{L}{\mathrm{a}}_{1-x}\mathrm{S}{\mathrm{r}}_x\mathrm{Ni}{\mathrm{O}}_2$ infinite-layer thin films, providing experimental evidence for understanding the scattering mechanisms of nickelates.

To investigate the intrinsic magnetic properties of ${\mathrm{UTe}}_2$, we performed ${}^{125}\mathrm{Te}$-NMR measurements on the ultraclean single-crystalline ${\mathrm{UTe}}_2$ with superconducting transition temperature $T_{\mathrm{c}}=2.1$ K and compared the results with those of the $T_{\mathrm{c}}=1.6$ K sample. The broadening of the linewidth of the NMR spectrum in the $a$-axis magnetic field and the low-temperature magnetic fluctuations observed in the 1.6 K sample are suppressed in the ultraclean sample, indicating that such magnetic properties originate from a tiny amount of U deficiency. The present results suggest that the magnetic properties in ${\mathrm{UTe}}_2$ are sensitive to the U deficiency. We also observed a peculiar angular dependence of the NMR quantities due to large magnetic anisotropy with the $a$ axis as the magnetic easy axis.

We present a method for generating hexagonal aperiodic tilings that are topologically equivalent to the triangular and dice lattices. This approach incorporates aperiodic sequences into the spacing between three sets of grids for the triangular lattice, resulting in “modulated triangular lattices.” Subsequently, by replacing the triangles with rhombuses, parallelograms, or hexagons, modulated dice or honeycomb lattices are constructed. Using the generalized Fibonacci, Thue-Morse, and tribonacci sequences, we demonstrate several examples of hexagonal aperiodic tilings. Structural analysis confirms that their diffraction patterns reflect the properties of the one-dimensional aperiodic sequences, namely, pure point (Bragg peaks) or singular continuous. Our method establishes a general framework for constructing a broad range of hexagonal aperiodic systems, advancing aperiodic-crystal research into higher dimensions that were previously focused on one-dimensional aperiodic sequences.

We report on the structural verification of metastable ice VII solidifying in the phase space of ice VI at 1.80 GPa at room temperature. Using time-resolved (TR) x-ray diffraction and TR ruby luminescence paired with high-speed microphotography utilizing a dynamic diamond anvil cell, an initial compression rate range from 0.12 to 95.84 GPa/s was explored. The solidification pressure of metastable ice VII has a potential sigmoidal dependence upon compression rate with a turnover compression rate of ∼80 GPa/s. The preferred crystallization of ice VII in the stability field of ice VI is due to the increased nucleation rate of ice VII over ice VI at 1.77 GPa that is driven by the surface energy difference between the liquid and solid phases along with the change in Gibbs free energy of solidification. The dynamic pressure-volume–compression behaviors of ice phases (VI and VII) show a lattice stiffening in both phases, especially during the compression loading. It is also found that the compression rate greatly affects the solid-solid phase transition between ice VI and VII but does not affect the liquid-solid transition between water and ice VI as much. Lastly, a third phase transition was found to occur after metastable ice VII transforms into high-density amorphous (HDA) ice, which could be a disordered hydrogen-bonded network configuration of ice VII forming out of HDA ice facilitated by the decoupling of the oxygen movement and reorientation of the ${\mathrm{H}}_2\mathrm{O}$ molecule. These results demonstrate the complexity of a seemingly simple molecule ${\mathrm{H}}_2\mathrm{O}$, how it can readily change its static properties with the modification of (de)compression rate, and highlight the need to use multiple TR structural and spectroscopic probes at higher time resolutions to realize the most comprehensive understanding.

We propose a geometric series modulated non-Hermitian quasiperiodic lattice model, and explore its localization and topological properties. The results show that with the ever-increasing summation terms of the geometric series, multiple mobility edges and non-Hermitian point gaps with high winding number can be induced in the system. The point gap spectrum of the system has a multiloop nested structure in the complex plane, resulting in a high winding number. In addition, we analyze the limit case of summation of infinite terms. The results show that the mobility edges merge together as only one mobility edge when summation terms are pushed to the limit. Meanwhile, the corresponding point gaps are merged into a ring with winding number equal to 1. Through Avila's global theory, we give an analytical expression for mobility edges in the limit of infinite summation, reconfirming that mobility edges and point gaps do merge and will result in a winding number that is indeed equal to 1.

We consider the dynamics of generic chaotic quantum many-body systems with no conservation laws, subject to weak bulk dissipation. It was recently observed [T. Mori, Phys. Rev. B 109, 064311 (2024)] that the generator of these dissipative dynamics, a quantum channel $\mathcal{E}$, retains a nonzero gap as the dissipation strength $\gamma \to 0$ if the thermodynamic limit is taken first. We use a hydrodynamic description of operator spreading in the presence of dissipation to estimate the gap of $\mathcal{E}$ as $\gamma \to 0$, to calculate the operator-size distribution of the slowest eigenmodes of $\mathcal{E}$, and to relate the gap to the long-time decay rates of autocorrelation functions under unitary Floquet dynamics. We provide a microscopic derivation of this hydrodynamic perspective for random unitary circuits. We argue that the gap in the $\gamma \to 0$ limit can change nonanalytically as one tunes the parameters of the unitary dynamics.

We study the photoconductivity response of graphene nanoribbons with armchair edges in the presence of dissipation using a Lindblad–von Neumann master equation formalism. We propose to control the transport properties by illuminating the system with light that is linearly polarized along the finite direction of the nanoribbon while probing along the extended direction. We demonstrate that the largest steady-state photocurrent occurs for a driving frequency that is slightly blue detuned to the electronic band gap proportional to the width of the nanoribbon. We compare the photoconductivity in the presence of coherent and incoherent light and conclude that the enhancement of the photoconductivity for blue-detuned driving relies on the coherence of the driving term. Based on this result, we propose a switching protocol for fast control of the photocurrent on a timescale of a few picoseconds. Furthermore, we suggest a design for a heterostructure of a graphene nanoribbon and a high-$T_c$ superconductor that is operated as a transistor as a step towards next-generation coherent electronics.

The Dzyaloshinskii-Moriya interaction (DMI) mediated by itinerant electrons with Rashba spin-orbit coupling (SOC) is calculated with particular attention to the effects of inplane magnetization component. Compared to the case of perpendicular magnetization, reported previously, the calculations are more intricate because of lower symmetry, but provide several new aspects; (i) The distinction between the DMI coefficients in free energy ($D$) and spin wave dispersion ($D^{\left(2\right)}$), pointed out in the previous paper, becomes a physically observable problem; (ii) The DMI coefficients remain vanishing when both the upper and lower bands have a Fermi surface; (iii) With inplane magnetization and strong SOC, $D^{\left(2\right)}$ is discontinuous across the Dirac point; (iv) At weak and moderate SOC (or large magnetization), $D$ has a cusp singularity, reflecting a stronger van Hove singularity at smaller magnetization. Finally, a comment is given to recent claims of finding terms other than the Lifshitz invariant.

Understanding coupled electron-phonon systems is one of the fundamental issues in strongly correlated systems. In this paper, we aim to extend the notion of mixed-state phases to the realm of coupled electron/spin-phonon systems. Specifically, we consider a two-dimensional cluster Hamiltonian locally coupled to a set of single bosonic modes with arbitrary coupling strength. First, we adopt a pure-state framework and examine whether a ground-state phase transition out of the symmetry-protected topological phase can be captured using the standard polaron unitary transformation. This approach involves restricting the analysis to the low-energy manifold of the phonon degrees of freedom. We find that the pure-state approach fails to detect the anticipated transition to a topologically trivial phase at strong spin-phonon coupling. Next, we turn to a mixed-state picture. Here, we analyze mixed states of the model obtained by tracing out the phonon degrees of freedom. We employ two distinct diagnostics for mixed-state phase transitions: (i) the von Neumann conditional mutual information (CMI) and (ii) the Rényi-2 CMI. We argue that both measures detect signatures of mixed-state phase transitions, albeit at different critical spin-phonon coupling strengths, each corresponding to a subtly distinct notion of the mixed-state phases.

We propose a range-separated hybrid exchange-correlation functional to calculate solid-state material properties. The functional mixes Hartree-Fock exchange with the semilocal exchange of the meta-generalized gradient approximation (meta-GGA) and the fraction of Hartree-Fock exchange is determined from the dielectric function. First-principles calculations and comparison with other meta-GGA approximations show that the functional leads to reasonably good performance for the band-gap and optical properties. We also show that the present functional also successfully resolves the well-known “band-gap problem” of narrow-gap Cu-based semiconductors, such as ${\mathrm{Cu}}_3{\mathrm{SbSe}}_4$ and ${\mathrm{Cu}}_3{\mathrm{AsSe}}_4$, where, in general, a considerably large band inversion energy leads to a “false” negative or metallic band gap for all other methods. Furthermore, reasonable accuracy for the occupied $d$ bands and transition energies is also obtained for bulk solids. Thus, overall, our results demonstrate the predictive power of range-separated meta-GGA hybrid functionals for quantum materials simulations.

Producing currents predominantly from a single valley, namely, valley-polarized currents, at optical-cycle timescales is an important aspect of the petahertz valleytronics, yet it remains less developed. This work exhibits the feasibility of achieving this goal using bichromatic optical fields, which allow for the precise control of subcycle electron dynamics. The combined effect of the helical and asymmetric waveforms of the optical fields leads to highly asymmetric excitation at different valleys and displacement of the excited electrons concurrently, thereby inducing valley-polarized currents with high valley purity, on the sub-optical-cycle timescale. Inherently, the purity of the currents built up from the optical approach remains high even for materials with short decoherence time. Moreover, the direction of the currents can be precisely controlled by adjusting the relative phase of the bichromatic components. Our work offers a promising avenue for generating and modulating high-purity valley-polarized currents at the femtosecond timescale, facilitating the development of petahertz valleytronics.

Higher-order phononic topology has garnered significant attention in recent years, with many novel phonon topological modes that have been unveiled. However, the exploration of efficient control of phononic higher-order topology in crystalline materials is rarely reported. In the present work, we demonstrate that strain and twist can effectively manipulate the phonon topological properties of materials. Specifically, by applying strain to the $1T\text{−}{\mathrm{HfTe}}_2$ monolayer and twisting the AAA-stacked (all three layers are perfectly aligned without relative displacement or rotation) ${\mathrm{HfTe}}_2$ trilayer, the phonon bands in both systems transition from topologically trivial to nontrivial. Phononic higher-order topology is characterized by the fractional quadrupole in the strained $1T\text{−}{\mathrm{HfTe}}_2$ monolayer, and by the fractional bulk dipole polarization in the ${\mathrm{HfTe}}_2$ twisted smallest moiré inversion lattice. Our work not only offers strategies for searching topological phonon modes, but also provides insights into controlling phononic higher-order topology in crystalline materials.

The recently delimited altermagnetic phase is characterized by zero net magnetization but momentum-dependent collinear spin splitting. To explore the intriguing physical effects and potential applications of altermagnets, it is essential to analyze their Fermi surface properties, encompassing both configurations and spin textures. Here, we conduct a Fermiology study on metallic altermagnets and demonstrate that the collinear spin-split features of their Fermi surfaces can be clearly revealed through quantum oscillation measurements. By introducing a transverse Zeeman field to remove the spin-degenerate lines in the momentum space, the Fermi surface undergoes a Lifshitz transition, giving rise to spin-flipped cyclotron motion between orbits with opposite spins. Accordingly, the Onsager-Lifshitz quantization yields two sets of Landau levels, leading to frequency splitting of the Shubnikov–de Haas oscillations in conductivity. In the presence of spin-orbit coupling, the Zeeman field causes two separate cyclotron orbits to merge at the Lifshitz transition point before splitting again. This results in the two original frequencies discontinuously changing into a single frequency equal to their sum. Our work unveils a unique and universal signature of altermagnetic Fermi surfaces that can be probed through quantum oscillation measurements.

Numerical methods capable of handling nonequilibrium impurity models are essential for the study of transport problems and the solution of the nonequilibrium dynamical mean-field theory (DMFT) equations. In the strong correlation regime, the self-consistently resummed hybridization expansion is an appealing strategy, which however has been employed so far mainly in the lowest-order noncrossing approximation. At higher orders, standard implementations become numerically costly, but a significant speed-up can be achieved by evaluating multidimensional integrals in an approximate factorized form. Here we develop a one-crossing approximation solver based on the recently introduced quantics tensor cross interpolation, and demonstrate its accuracy and efficiency with applications to the Anderson impurity model and nonequilibrium steady-state DMFT calculations for the Hubbard model.

We use first-principles scattering calculations based upon wave-function matching and implemented with a tight-binding muffin-tin orbital basis to evaluate the orbital Hall conductivity ${\sigma }_{\mathrm{oH}}$ for Ti, V, Cr, Cu, and Pt metals with temperature-induced lattice disorder. Only interatomic fluxes of orbital angular momentum are included in these estimates; intra-atomic fluxes, which do not contribute to the transfer of angular momentum are explicitly excluded. The resistivity and orbital Hall angle are both found to be linear in temperature so ${\sigma }_{\mathrm{oH}}$ is at most weakly temperature dependent. The value of ${\sigma }_{\mathrm{oH}}$ we obtain for bulk Cr is $\approx 2\times {10}^3(\hslash /e){\left(\mathrm{\Omega }\mathrm{cm}\right)}^{-1}$, which is substantially lower than previously obtained theoretical results (but in better agreement with values extracted from experiment). In units of ${10}^3(\hslash /e){\left(\mathrm{\Omega }\mathrm{cm}\right)}^{-1}$, the values obtained for Ti, V, and Pt are 5, 6, and 7, respectively.