Topological nodal-line semimetals represent a unique class of materials with intriguing electronic structures and rich of symmetries, hosting electronic states with nontrivial topological properties. Among these, $\mathrm{ZrA}{\mathrm{s}}_2$ stands out, characterized by its nodal lines in a momentum space, governed by nonsymmorphic symmetries. This study integrates angle-resolved photoemission spectroscopy (ARPES) with density functional theory (DFT) calculations to explore the electronic states of $\mathrm{ZrA}{\mathrm{s}}_2$. Our study provides experimental evidence of nonsymmorphic symmetry-protected band crossing and nodal lines in $\mathrm{ZrA}{\mathrm{s}}_2$. In ARPES scans, we observed a distinctive surface and bulk states at different photon energies associated with nodal lines. Our results, supported by calculations based on DFT, unveil such impervious band crossing anchored at specific points in the Brillouin zone, with particular emphasis on the $S$ point. Surface bands and bulk states near the crossing are elucidated through slab calculations, corroborating experimental findings. These findings enhance our understanding of the electronic structure of $\mathrm{ZrA}{\mathrm{s}}_2$.

Measurement-based entanglement (MBE) is a method for entangling quantum systems through the state projection that accompanies a parity measurement. We derive a stochastic master equation describing measurement-based entanglement of a pair of silicon double-dot flopping-mode spin qubits, develop numerical simulations to model this process, and explore what modifications could enable an experimental implementation of such a protocol. With device parameters corresponding to current qubit and cavity designs, we predict an overlap of the final state of the MBE protocol with the target Bell state $|{\mathrm{\Psi }}_{+}\rangle$ of $\approx 61\%$. By increasing the cavity outcoupling rate by a factor of 10, we are able to obtain an improvement of this metric to $\approx 81\%$ while maintaining a yield of 33%.

Two-dimensional (2D) ferroelectricity has attracted considerable interest since its demonstration in van der Waals monolayers. Research on 2D ferroelectricity has so far focused on van der Waals materials, and whether some of the intrinsic ferroelectric mechanisms found in perovskite bulks can be retained to the monolayer limit remains an issue to be solved. Here, we demonstrate that intrinsic ferroelectricity caused by the lone pair electron effect can exist in the inorganic halide perovskite monolayers. This ferroelectricity occurs in halide perovskite monolayers with smaller anions, involving ${\mathrm{Cs}}_2{\mathrm{GeF}}_4, {\mathrm{Cs}}_2{\mathrm{SnF}}_4$, and ${\mathrm{Cs}}_2{\mathrm{SnCl}}_4$. The first two are direct band-gap semiconductors while the latter is an indirect band-gap semiconductor. The octahedral tilt mode also appears in the ground-state structures of these 2D ferroelectrics. The ferroelectric monolayers containing ${\mathrm{F}}^{-}$ ions have relatively greater ferroelectric polarization, but also have a higher-energy barrier for ferroelectric switching. This work helps to design 2D ferroelectricity beyond van der Waals materials.

Optical bound states in the continuum (BICs) exist commonly in periodic structures with strong local resonances. Merging multiple BICs provides an excellent way to further enhance the $Q$ factor of nearby quasi-BICs compared with isolated BICs. Here, we report on the giant and angle-insensitive transmitted optical Goos-Hänchen shift (GHS) through a photonic crystal slab, assisted by the ultrahigh-Q quasi-BICs on a quasiflat band with embedded tunable merging BICs at a nearly arbitrary wave vector in the reciprocal space. Even at large angles of incidence, GHS can also be enhanced to >4 orders of wavelength by the designed tunable off-$\mathrm{\Gamma }$ merging BICs. Empowered by the angle-insensitive ultrahigh-$Q$ resonances, the wide-angle giant GHS within an extremely narrow bandwidth is realized. Furthermore, we propose an ultrasensitive environmental refractive index sensor and a temperature sensor based on the enhanced GHS by merging BICs. Our work reveals the tremendous potential of tunable merging BICs for various applications based on angular selectivity, such as beam steering, directional vector beams, and angle-multiplexed sensors.

Taken together, time-reversal and spatial inversion symmetries impose a twofold spin degeneracy of the electronic states in crystals. In centrosymmetric materials, this degeneracy can be lifted by introducing magnetism, either via an externally applied field or through internal magnetization. However, a correlated alignment of spins, even in the paramagnetic phase, can lift the spin degeneracy of electronic states. Here, we report an in-depth study of the electronic band structure of the Eu-ternary pnictide ${\mathrm{EuZn}}_2{\mathrm{Sb}}_2$ through a combination of high-resolution angle-resolved photoemission spectroscopy measurements and first-principles calculations. An analysis of the photoemission line shapes over a range of incident photon energies and sample temperatures is shown to reveal the presence of band spin-degeneracy lifting in the paramagnetic phase. Our angle-resolved photoemission spectroscopy results are in good agreement with theoretical ferromagnetic-phase calculations, which indicates the importance of ferromagnetic fluctuations in the system. Through our calculations, we predict that spin-polarized bands in ${\mathrm{EuZn}}_2{\mathrm{Sb}}_2$ generate a single pair of Weyl nodes. Our observation of band splitting in ${\mathrm{EuZn}}_2{\mathrm{Sb}}_2$ provides a key step toward realizing time-reversal symmetry breaking physics in the absence of long-range magnetic order.

Microscopically understanding competing orders in strongly correlated systems is a key challenge in modern quantum many-body physics. For example, the study of magnetic polarons and their relation to pairing in the Fermi-Hubbard model in different geometries remains one of the central questions, and may help to understand the mechanism underlying unconventional superconductivity in cuprates or transition metal dichalcogenides. With recent advances in analog quantum simulation of the Fermi-Hubbard model on nonbipartite lattices, frustrated physics can now be explored experimentally in systems lacking particle-hole symmetry. Here, we study the singly doped $t-J$ model on the triangular lattice, focusing on the competition between kinetic and magnetic frustration as a function of temperature. In doublon doped systems, we uncover a crossover between Nagaoka-type ferromagnetic (FM) correlations at high temperature and exchange mediated antiferromagnetic (AFM) order around the doublon at low temperature. For hole-doped systems, kinetic Haerter-Shastry-type AFM at high temperature as well as exchange interactions at low temperature favor ${120}^{\circ }$ order, strengthening magnetic correlations compared to the undoped system. In the ground state, the presence of AFM correlations throughout a wide range of interactions indicates confinement of both types of dopants. In this regime we firmly establish the presence of linear confining potentials via energy scaling arguments, supporting the picture of geometric strings in the frustrated triangular $t-J$ model.

At low temperatures, the transport coefficients in the disordered electron gas acquire quantum corrections as a result of the complex interplay of disorder and interactions. The interaction corrections to the electric conductivity have their origin in virtual processes with typical electronic energies far exceeding the temperature. Here, we study interaction corrections $\delta S$ to the thermopower $S$ of the two-dimensional disordered electron gas with long-range Coulomb interactions. We show that while both real and virtual processes contribute to these corrections, the real processes are dominant and lead to a logarithmic temperature dependence of $\delta S/S$ with $\delta S/S<0$.

Hydrogen bonds play a crucial role in the anomalous behavior of water. While the properties of individual hydrogen bonds have been extensively studied, the topological characteristics of the resulting hydrogen bond network remain less explored. In this study, we employ molecular dynamics simulations to examine various aqueous interfaces, uncovering an increased number of hydrogen bonds parallel to surfaces compared to bulk water. To quantify the topology of these networks, we introduce estimators for network percolation and dimensionality. Our findings reveal that the elevated proportion of hydrogen bonds parallel to the interface significantly influences network connectivity, reducing both the number of water layers and the distance from the surface at which the network achieves full connectivity. Consequently, hydrogen bond networks at interfaces exhibit more “two-dimensional” characteristics than those in bulk water due to high local water density and the competition between water-water hydrogen bonds and water-surface interactions.

Two-dimensional (2D) layered materials, whether in bulk form or reduced to just a single layer, have potential applications in spintronics and capacity for advanced quantum phenomena. A prerequisite for harnessing these opportunities lies in gaining a comprehensive understanding of the spin behavior in 2D materials. The low dimensionality motivates an understanding of the spin correlations over a wide length scale, from local to long-range order. In this context, we focus on the magnetism in bulk ${\mathrm{MnPSe}}_3$ and ${\mathrm{MnPS}}_3$, 2D layered van der Waals antiferromagnetic semiconductors. These materials have similar honeycomb Mn layers and magnetic ordering temperatures, but distinct spin orientations and exchange interactions. We utilize neutron scattering to gain deeper insights into the local magnetic structures and spin correlations in the paramagnetic and ordered phases by systematically investigating a ${\mathrm{MnPS}}_x{\mathrm{Se}}_{3-x}$ $(x=0, 1, 1.5, 2, 3)$ series of powder samples using total neutron scattering measurements. By employing magnetic pair distribution function analysis, we unraveled the short-range magnetic correlations in these materials and explored how the nonmagnetic anion S/Se mixing impacts the magnetic correlations. The results reveal that the magnetism can be gradually tuned through alteration of the nonmagnetic S/Se content, which tunes the atomic structure. The change in magnetic structure is also accompanied by a control of the magnetic correlation length within the 2D honeycomb layers. Complimentary inelastic neutron scattering measurements allowed a quantification of the change in the magnetic exchange interactions for the series and further highlighted the gradual evolution of spin interactions in the series ${\mathrm{MnPS}}_x{\mathrm{Se}}_{3-x}$.

A lightly doped single-band Hubbard model on a two-leg ladder exhibits a Luther-Emery phase, whereas the three-band Hubbard ladder behaves as a Luttinger liquid upon hole doping. To understand this discrepancy, we present a systematic density-matrix renormalization group study of the three-band Hubbard model on two-leg cylinders with further-neighbor particle hoppings. The inclusion of the longer-range hopping is motivated by the studies of the single-band Hubbard model in which the further-neighbor hopping terms are suggested to be crucial for the unconventional superconductivity. When the longer-range hopping parameters are small, the ground state is a Luttinger liquid having mutually commensurate superconducting, charge, and spin density wave correlations. Increasing the longer-range hopping drives a transition into a Luther-Emery phase with quasi-long-ranged superconducting and charge orders but short-ranged spin-spin correlations. By down-folding the three-band Hubbard model into an effective $t\text{−}{t}^{\prime }\text{−}J\text{−}{J}^{\prime }$ model, we find that in the Luther-Emery phase, both the nearest- and second-neighbor kinetic energies are enhanced due to an effective increase of copper-oxygen hybridization. Amplifying intercell oxygen orbital hopping mirrors the benefits of reducing the charge transfer energy, causing doped holes to favor oxygen orbitals and strengthening superconducting pairing.

We present a comprehensive investigation of superconducting properties in the Chevrel phase compound ${\mathrm{PbMo}}_6{\mathrm{Se}}_8$ by x-ray diffraction, dc magnetization, resistivity, heat capacity, and magnetic relaxation experiments. We determine a bulk superconducting transition temperature $T_{\mathrm{c}}$ of 3.8 K. Key superconducting parameters such as lower $\left[{\mu }_0{H}_{c1}\left(0\right)\right]$ and upper $\left[{\mu }_0{H}_{c2}\left(0\right)\right]$ critical fields, coherence length $\left[{\xi }_{\text{GL}}\left(0\right)\right]$, penetration depth $\left[{\lambda }_{\text{GL}}\left(0\right)\right]$, Ginzburg-Landau parameter $\left(\kappa \right)$, Pauli paramagnetic field $\left({\mu }_0{H}_P^{\text{str}}\right)$, and Maki parameter $\left({\alpha }_M\right)$ are obtained. The BCS model provides a reasonable description of the heat-capacity data. An unconventional vortex state is evident from the investigation of the unusual fishtail effect and nonmonotonous magnetic field dependency of the vortex pinning energy obtained from the magnetic relaxation experiments, indicating a deviation from the ideal type II superconducting vortex, in ${\mathrm{PbMo}}_6{\mathrm{Se}}_8$. A detailed ${\mu }_0\mathrm{H}$-T phase diagram has been drawn illustrating a multiphase vortex crossover.

A qubit suffers decoherence when coupled to a classical or quantum environment, and characterizing the qubit decoherence process is vital in quantum technologies. Repetitive Ramsey interferometry measurements (RIMs) are often used to measure qubit coherence, assuming that the environment remains unaffected after each measurement and the outcomes of all measurements are independent and identically distributed (i.i.d.). While this assumption is valid for a classical environment, it may not hold for a quantum environment due to the non-negligible backaction from qubit to environment, especially when the environment has a memory time much longer than the duration of each RIM cycle. Here, we present a general theoretical framework to incorporate the measurement backaction from qubit to environment in sequential RIMs. We show that a RIM of a qubit induces a quantum channel on the quantum environment, and sequential RIMs gradually steer the quantum environment to the fixed points of the channel. We reveal three distinct environment steering effects—polarization, depolarization, and metastable polarization, depending on the commutativity of the noise operator $B$ and the free environment Hamiltonian $H_e$: (1) If $B$ commutes with $H_e$, i.e., $[B,H_e]=0$, the quantum environment is gradually polarized to different eigenstates of $B$ as the number $m$ of repetitive RIMs increases; (2) when $[B,H_e]\ne 0$, the quantum environment is gradually depolarized to a maximally mixed state of its whole Hilbert space or a Hilbert subspace; (3) when $[B,H_e]\ne 0$ but one of $H_e$ and $B$ is a small perturbation on the other, metastable polarization can happen, such that the quantum environment is first polarized for a finite range of $m$ but becomes gradually depolarized as $m$ increases further. The environment steering also makes the measurement statistics of sequential RIMs develop non-i.i.d. features, such that the measurement result distribution can display multiple peaks for a small quantum environment, corresponding to different fixed points of the quantum channel. Realistic examples of central spin models are presented to demonstrate the measurement statistics and environment steering effects. Our paper not only elucidates the measurement backaction and statistics of repetitive qubit coherence measurements, but is also useful for designing protocols to engineer the state or dynamics of a quantum environment with a qubit ancilla.

Decoherence and relaxation of solid-state defect qutrits near a crystal surface, where they are commonly used as quantum sensors, originate from charge and magnetic field noise. A complete theory requires a formalism for decoherence and relaxation that includes all Hamiltonian terms allowed by the defect's point-group symmetry. This formalism, presented here for the $C_{3v}$ symmetry of a spin-1 defect in a diamond, silicon carbide, or similar host, relies on a Lindblad dynamical equation and clarifies the relative contributions of charge and spin noise to relaxation and decoherence, along with their dependence on the defect spin's depth and resonant frequencies. The calculations agree with the experimental measurements of Sangtawesin et al. [Phys. Rev. X 9, 031052 (2019)], and corroborate the importance of charge noise.

In this work, we explore the generalities of the supercurrent diode effect. As an illustrative example, we examine a model of a two-dimensional superconductor with Rashba-type spin-orbit coupling under an in-plane magnetic field and in the clean limit, which realizes a helical phase. First, we utilize Ginzburg-Landau phenomenology to derive a general formula for the diode efficiency. This is achieved by incorporating higher gradient terms in the Lifshitz invariants, which are responsible for the nonreciprocal superflow. Subsequently, we validate these results through microscopic diagrammatic computation and further estimate correction terms arising from interband pairing correlations. We provide a detailed comparison to prior investigations of this problem conducted within the framework of the quasiclassical approximation based on the Eilenberger equation.

It is well established that the presence of single impurity can have a substantial impact on the transport properties of quantum many-body systems at low temperature. In this work, we investigate a close analog of this problem from the perspective of quantum information dynamics. We construct Brownian circuits and Clifford circuits consisting of a free fermion hopping term and a sole interaction. In both circuits, our findings reveal the emergence of operator scrambling. Notably, the growth of the operator can be mapped to the symmetric exclusion process in the presence of a source term localized at a single point. We demonstrate that in the one-dimensional system, both the operator and entanglement exhibit diffusive scaling. Conversely, in scenarios characterized by all-to-all hopping, the operator's size undergoes exponential growth, while the entanglement exhibits a linear increase over time.

Antiferromagnetic (AFM) topological insulators (TIs), which host magnetically gapped Dirac-cone surface states and exhibit many exotic physical phenomena, have attracted great attention. Here, we find that the coupled surface states can be intertwined to give birth to a set of $2n$ unique new Dirac cones, dubbed intertwined Dirac cones, through the anisotropic coupling enforced by crystalline $n$-fold ($n=2,3,4,6$) rotation symmetry $C_{nz}$ in the presence of a $PT$-symmetry breaking potential, for example, an electric field. Interestingly, we also find that the warping effect further drives the intertwined Dirac-cone state into a quantum anomalous Hall phase with a high Chern number ($C=n$). Then, based on first-principles calculations, we have explicitly demonstrated six intertwined Dirac cones and a Chern insulating phase with a high Chern number ($C=3$) in ${\mathrm{MnBi}}_2{\mathrm{Te}}_4/{\left({\mathrm{Bi}}_2{\mathrm{Te}}_3\right)}_{\mathrm{m}}/{\mathrm{MnBi}}_2{\mathrm{Te}}_4$ heterostructures, as well as the $C=2$ and $C=4$ phases in HgS and $\alpha \text{−}{\mathrm{Ag}}_2\mathrm{Te}$ films, respectively. This work discovers the intertwined Dirac-cone state in AFM TI thin films, which reveals a mechanism for designing the quantum anomalous Hall state with a high Chern number and also paves a way for studying highly tunable high-Chen-number flat bands of twistronics.

The synergy of strong spin-orbit coupling and electron-electron interactions gives rise to unconventional topological states, such as topological Mott insulator, Weyl semimetal, and quantum spin liquid. In this study, we have grown single crystals of the pyrochlore iridate ${\mathrm{Pr}}_2{\mathrm{Ir}}_2{\mathrm{O}}_7$ and explored its magnetic, lattice dynamical, and electronic properties. While Raman spectroscopy data reveal six phonon modes confirming the cubic $\mathrm{Fd}\overline{3}\mathrm{m}$ crystal symmetry, dc magnetic susceptibility data show no anomalies and hence indicate the absence of magnetic phase transitions down to 2 K. Both temperature-dependent electric transport and optical conductivity data reveal the metallic character of ${\mathrm{Pr}}_2{\mathrm{Ir}}_2{\mathrm{O}}_7$. The optical conductivity spectrum contains a midinfrared absorption band, which becomes more pronounced with decreasing temperature due to spectral weight transfer from high to low energies. The presence of the midinfrared band hints at the importance of correlation physics. The optical response furthermore suggests that ${\mathrm{Pr}}_2{\mathrm{Ir}}_2{\mathrm{O}}_7$ is close to the Weyl semimetal phase.

The magnetic Weyl semimetal ${\mathrm{Co}}_3{\mathrm{Sn}}_2{\mathrm{S}}_2$ is extensively investigated due to its giant anomalous Hall effect (AHE). Recent studies demonstrate that the AHE can be effectively tuned by multielectron Ni doping. To reveal the underlying mechanism of this significant manipulation, it is crucial to explore the band-structure modification caused by Ni doping. Here, we study the electrodynamics of both pristine and Ni-doped ${\mathrm{Co}}_{3-x}{\mathrm{Ni}}_x{\mathrm{Sn}}_2{\mathrm{S}}_2$ with $x=0$, 0.11, and 0.17 by infrared spectroscopy. We find that the inverted energy gap around the Fermi level $\left(E_F\right)$ gets smaller at $x=0.11$, which is supposed to enhance the Berry curvature and therefore increases the AHE. Then $E_F$ moves out of this gap at $x=0.17$. We also observe the evidence of band broadening caused by doping. Our results provide detailed information about the band structure of ${\mathrm{Co}}_{3-x}{\mathrm{Ni}}_x{\mathrm{Sn}}_2{\mathrm{S}}_2$ at different doping levels, which will help to guide further studies on the chemical tuning of AHE.