The influence of twist angles on the thermal transport properties of bilayer graphene has attracted considerable attention within the scientific community. However, the relationship between twist angle and phonon hydrodynamics remains insufficiently explored. Additionally, the limitations of empirical potential fields have often restricted the accuracy of previous calculations. In this study, we systematically examine the effect of twist angle on phonon hydrodynamics in twisted bilayer graphene using a machine learned neuroevolution potential combined with the Boltzmann transport equation. Our results reveal a distinctive “$\mathsf{V}$-shaped” trend in thermal conductivity, driven by variations in N-type and U-type phonon scattering rates, underscoring the significant influence of twist angle on phonon hydrodynamics. Particularly, the flexural mode plays a critical role, with its contribution to thermal conductivity decreasing as the twist angle changes. This analysis highlights the importance of machine learning potentials in accurately capturing interlayer interactions, providing a more precise understanding of thermal transport in two-dimensional materials and offering alternative possibilities for material manipulation.

We establish a duality between open many-body systems governed by the Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) equation and satisfying the detailed balance condition on the one side, and closed bilayer systems with a self-adjoint Hamiltonian on the other side. Under this duality, the identity operator on the open-system side maps to a quantum many-body scar of the dual Hamiltonian $\mathcal{H}$. This scar eigenstate has a form of a thermofield double state for a single-body conserved quantity entering the detailed balance conditions. A remarkable feature of this thermofield scar is a tunable single-layer entanglement entropy controlled by the reservoir temperature on the open-system side. Further, we identify broad classes of many-body open systems with nontrivial explicit eigenoperators $Q$ of the Lindbladian superoperator. The expectation values of the corresponding observables exhibit a simple exponential decay, ${\langle Q\rangle }_t=e^{-\mathrm{\Gamma }t}{\langle Q\rangle }_0$, irrespectively of the initial state. Under the above duality, these eigenoperators give rise to additional (towers of) scars. Finally, we point out that more general superoperators (not necessarily of the GKSL form) can be mapped to self-adjoint Hamiltonians of bilayer systems harboring scars and provide an example thereof.

We show that the combined effects of a dynamical Coulomb blockade and integer quantum Hall effect in a coupled hybrid metal-semiconductor setup provide a pathway for realizing resonant tunneling in Luttinger liquids. This hybrid setup can be brought to the quantum critical regime by varying gate voltages and contact resistances. We explore the nature of quantum criticality, Kondo effect, charge fractionalization, and transport in such a hybrid setup, and verify their robust non-Fermi-liquid behaviors. Our work opens a promising route for quantum simulating exotic zero-temperature quantum critical phenomena associated with Luttinger-liquid physics in a nanoengineered electronic circuit with well-defined quantum Hall channels.

Geometrically frustrated materials with kagome lattices have garnered significant research interest due to their unique topological properties and exotic magnetic behavior. Among these kagome materials, $\mathrm{C}{\mathrm{o}}_2{\left(\mathrm{OH}\right)}_3\mathrm{Cl}$ stands out for its pronounced crystal field effect, which invokes the highly pursued exploration of the interplay among the crystal structure, coordination environment, and electronic behavior. In this paper, pure-phase $\mathrm{C}{\mathrm{o}}_2{\left(\mathrm{OH}\right)}_3\mathrm{Cl}$ nanoparticles were successfully synthesized via a hydrothermal reaction. The morphology, crystal structure, and bonding characteristics were comprehensively characterized at ambient conditions. Low-temperature magnetic measurements revealed a ferromagnetic transition at $\sim 10$ K. The structural evolution of $\mathrm{C}{\mathrm{o}}_2{\left(\mathrm{OH}\right)}_3\mathrm{Cl}$ upon compression was further investigated using in situ high-pressure synchrotron x-ray diffraction (XRD). At 10.8 GPa, an anomalous negative compression occurs along the $c$ axis. A structural transformation from the initial rhombohedral to the monoclinic phase has been uncovered at 13.5 GPa, accompanied by a significant increase in bulk modulus. High-pressure Raman scattering and ultraviolet-visible absorption measurements indicated that the phase transition was driven by an increase in crystal field splitting energy ($\mathrm{\Delta }$), which enhanced the Jahn-Teller effect, altered the electronic configuration ($p-d$ hybridizations and $d\text{−}d$ transition) of $\mathrm{C}{\mathrm{o}}^{2+}$ ions, and potentially induced a transition from high- to low-spin states. In this paper, we provide insights into the mechanisms underlying structural transitions and electronic behavior in geometrically frustrated materials with kagome lattices under external pressures.

Emergent molecularlike excitations have been discovered in a series of pyrochlore antiferromagnets, yet their origins and relationships with the coexisting magnon excitations remain a puzzle. Here, by incorporating dynamic spin-lattice coupling through the site-phonon model, we accomplish a unified description of the molecular and magnon excitations, which allows us to provide a statistical interpretation of the molecularlike modes.

${\mathrm{CeRh}}_2{\mathrm{As}}_2$ shows the superconducting (SC) multiphase under the $c$-axis magnetic field, which is considered to originate from local inversion symmetry breaking at the Ce site. We reported that the antiferromagnetic (AFM) order is inside the SC phase and that the AFM state disappears at the transition field to the high-field SC phase. However, the magnetic structure in the AFM state has not been clarified yet. In this paper, we performed ${}^{75}\mathrm{As}$-NMR measurements in the SC phase in $H\parallel \left[110\right]$ to identify the magnetic structure. Comparing the NMR linewidth with $H\parallel c$, we found that the internal magnetic field is oriented to the $c$ axis. This suggests a $\mathit{q}=\mathit{0} A$-type AFM with the moments parallel to the $c$ axis. We also observed the reduction of the spin susceptibility, which indicates spin-singlet superconductivity in the low-field SC phase. This study provides an important clue to clarify the correlation between the SC multiphase, magnetism, and local inversion symmetry breaking.

We propose the pair-breaking scattering interference as a general source of coherence peak modulations in superconductors. Assuming this mechanism, we present a simple physical picture for the coherence peak modulations in overdoped cuprate ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{Ca}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{10+\delta }$ (Bi-2223), ferromagnetic iron pnictide ${\mathrm{EuRbFe}}_4{\mathrm{As}}_4$ (Eu-1144), and kagome metals $A{\mathrm{V}}_3{\mathrm{Sb}}_5$ ($A=$ K, Rb, and Cs). Specifically, we explain the wave vectors, the particle-hole symmetry, and the dependence on the internal or external Zeeman-field of the coherence peak modulations. This paper is intended as a cautious reminder to the scientific community when asserting the existence of a pair density wave phenomenon in the absence of tunneling conductance modulations in the normal state.

Majorana bound states emerge in topological superconductors as zero-energy edge states exhibiting spatial nonlocality. Despite the enormous advances, the detection of Majorana bound states is still challenging, mainly because topologically trivial Andreev bound states produce similar signatures. In this work, we consider a topological superconductor with Majorana bound states coupled to quantum dots and investigate the dynamics of their quantum correlations with the aim to explore their entanglement properties. In particular, we characterize entanglement by using concurrence and discord, which are also complemented by entanglement dynamics and return probability. We find that Majorana bound states at truly zero energy can transform an initially entangled system into its classical state, while they can create maximally entangled states at a finite energy overlap. Interestingly, we show that the system can generate a maximally entangled state between MBSs and a quantum dot by simply controlling the Majorana nonlocality. We demonstrate that these results hold in scenarios when the initial state is either maximally entangled or separable, albeit in the latter, maximally entangled states are achieved in the long time dynamics. Furthermore, we contrast our findings with those produced by a regular fermion and obtain very distinct entanglement signatures. Our work offers an alternative approach to characterizing Majorana bound states, which can also be useful towards their utilization for quantum information tasks.

The possibility of the quantum anomalous Hall effect (QAHE) in two-dimensional kagome systems with $d$-orbital electrons is studied within a multiorbital tight-binding model. We concentrate on the case of isotropic Slater-Koster integrals which is realized in a recently discovered class of metal-organic frameworks ${TM}_3{\mathrm{C}}_6{\mathrm{O}}_6$ with transition metals ($\mathit{TM}$) in the beginning of the $3d$ series. Furthermore, in the absence of exchange-type spin-orbit coupling, only isotropic Slater-Koster integrals give a perfect flatband in addition to the two dispersive bands hosting relativistic (Dirac) and quadratic band crossing points at high symmetry spots in the Brillouin zone. A quantized topological invariant requires a flux-creating spin-orbit coupling, giving Chern number (per spin sector) $C=1$ not only from the familiar Dirac points at the six corners of the Brillouin zone, but also from the quadratic band crossing point at the center $\mathrm{\Gamma }$. In the case of isotropic Slater-Koster integrals the on-site spin-orbit coupling (SOC) is ineffective in creating the QAHE and it is only the transfer or exchange-type SOC which can lead to a QAHE. Surprisingly, this QAHE comes from the nontrivial effective flux induced by the transverse part of the spin-orbit coupling, exhibited by electrons in the $d$-orbital state with $m_l=0$ ($d_{z^2}$ orbital), in stark contrast to the more familiar form of QAHE due to the $d$ orbitals with $m_l\ne 0$, driven by the Ising part of spin-orbit coupling. The $C=1$ Chern plateau (per spin sector) due to the Dirac point extends over a smaller region of Fermi energy than that due to quadratic band crossing. Our result hints at the promising potential of kagome $d$-electron systems as a platform for dissipationless electronics by virtue of its unique QAHE.

Rydberg excitons in transition metal dichalcogenides (TMDs) have emerged as a promising platform for investigating the properties of open quantum systems, thanks to their large binding energies (hundreds of milli-electron-volts). However, the study of Rydberg excitons in TMDs has been hindered by sample quality limitations, strong background signals from ground excitons, and broadening at room temperature. In this work, we report the first observation of multiple Rydberg exciton states in monolayer ${\mathrm{MoS}}_2$ at room temperature using Imbert-Fedorov (IF) shift spectroscopy. By numerically solving the Schrödinger equation, we extracted the quasiparticle band gaps for A and B excitons, confirming the temperature-induced redshift of the band gap, in excellent agreement with previous results. Our findings establish IF shift spectroscopy as a powerful tool for characterizing Rydberg excitons in TMDs, paving the way for potential applications in quantum manipulation and control.

In this paper, we demonstrate electric-field-induced band modification of an asymmetrically twisted doubly aligned bilayer graphene hBN (hBN/BLG/hBN) supermoiré lattice. Distinct from unaligned BLG/hBN systems, we observe regions in the density-displacement field $\left(n\text{−}D\right)$ plane where the device conductance is independent of $n$ and decreases as $\left|D\right|$ increases. This distinction arises due to the angle asymmetry between the layers, which induces field-controlled layer polarization. We identify $D$-dependent additional band gaps near the charge neutrality point that appear in the conduction (valence) band for negative (positive) $D$ values. In the quantum Hall regime, different sixfold degenerate Landau levels are observed. Our findings establish that in an asymmetric supermoiré heterostructure, an external vertical displacement field affects the valence and conduction bands very differently and sheds light on the asymmetric conductance patterns noted in previous studies.

Rare-earth tritellurides ($R\mathrm{T}{\mathrm{e}}_3$) are van der Waals (vdW) coupled semimetals ideal for exploring exotic electronic phases. $\mathrm{LaT}{\mathrm{e}}_3$ is especially important for understanding the fundamental fermiology of the $R\mathrm{T}{\mathrm{e}}_3$ family because it is nonmagnetic and has a simpler charge-density wave structure. In this study, we used spectroscopic-imaging scanning tunneling microscopy to measure the Landau levels of $\mathrm{LaT}{\mathrm{e}}_3$ with high-energy resolution at 300 mK. These measurements were taken under varying magnetic fields up to 15 T, with fine intervals of 0.02–0.03 T. Our results reveal a pair of pronounced electron-hole Fermi pockets of similar sizes and evidence of electron-boson coupling in both pockets. Given the strong charge susceptibility typical of low-dimensional conductors, the interactions and instabilities driven by the electron-hole Fermi pockets could be a basis for searching unexplored quantum phases in other antiferromagnetic $R\mathrm{T}{\mathrm{e}}_3$ compounds.

Langevin dynamics simulations are used to analyze the static and dynamic properties of an $XY$ model adapted to dimers forming on Si(001) surfaces. The numerics utilize high-performance parallel computation methods on GPUs. The static exponent $\nu$ of the symmetry-broken $XY$ model is determined to $\nu =1.04$. The dynamic critical exponent $z$ is determined to $z=2.13$ and, together with $\nu$, shows the behavior of the Ising universality class. For time-dependent temperatures, we observe frozen domains and compare their size distribution with predictions from Kibble-Zurek theory. We determine a significantly larger quench exponent that shows little dependence on the damping or the symmetry-breaking field.

Recently, significant theoretical and experimental progress on the nonlinear Hall effect has been achieved in graphene. However, the nonlinear Hall effect in other prototypical two-dimensional lattices, e.g., the kagome and Lieb lattices, remains unexplored. In this work, we investigate the nonlinear Hall effect in both the kagome and Lieb lattices with the staggered hopping and intrinsic spin-orbit coupling. In both systems, the staggered hopping breaks the inversion symmetry and gives rise to the nonlinear Hall effect characterized by the Berry curvature dipole. Interestingly, our findings reveal a distinct pattern of the nonlinear Hall effect in the kagome lattice, where the Berry curvature dipole remains stable when the strength of the staggered hopping varies. This scenario is different from that in the Lieb lattice, where the Berry curvature dipole is prominent only within a narrow window close to the phase transitions induced by the staggered hopping. Our discovery is helpful for future studies on the nonlinear Hall effect.

Poor man's Majoranas (PMMs) hold the promise to engineer Majorana bound states in a highly tunable setup consisting of a chain of quantum dots that are connected via superconductors. Due to recent progress in controlling the amplitudes of elastic cotunneling (ECT) and crossed Andreev reflection (CAR), two vital ingredients for PMMs, experimental investigations of PMMs have gained significant interest. Previously, analytic conditions for the “sweet spots” that result in PMMs have focused on systems with infinite Zeeman energy. Here, we derive analytically a sweet spot condition for PMMs in a system with finite Zeeman energy in the absence of Coulomb interaction. We then consider two numerical models, one in which ECT and CAR are transmitted via superconducting bulk states and one in which they are transmitted via an Andreev bound state. We demonstrate that the analytical sweet spot conditions can only be approximated in these more realistic models, but they cannot be satisfied exactly. As a consequence, we do not find perfect PMMs in these systems, but instead near-zero-energy states that are highly, but not perfectly, localized. These states can be considered as imperfect PMMs and their classification relies on threshold values, which adds some arbitrariness to the concept of PMMs.

The $z$-component of the Néel vector is measurable by the anomalous Hall conductivity in altermagnets because time reversal symmetry is broken. On the other hand, it is a nontrivial problem how to measure the in-plane component of the Néel vector. We study the second-order nonlinear conductivity of a system made of the $d$-wave altermagnet with the Rashba interaction. It is shown that the quantum-metric induced nonlinear conductivity and the nonlinear Drude conductivity are proportional to the in-plane component of the Néel vector, and hence, the in-plane component of the Néel vector is measurable. We obtain analytic formulas of the quantum-metric induced nonlinear conductivity and the nonlinear Drude conductivity both for the longitudinal and transverse conductivities. The quantum-metric induced nonlinear conductivity diverges at the Dirac point, while the nonlinear Drude conductivity is always finite. Hence, the quantum-metric induced nonlinear conductivity is dominant at the Dirac point irrespective of the relaxation time.

Achieving both ultrahigh quality $Q$ and high frequency simultaneously in mechanical resonators is challenging due to the positive correlation between loss and frequency. Graphene, a two-dimensional (2D) material with single-atomic-layer thickness and exceptional mechanical properties, is capable of satisfying the material requirements of emerging dissipation dilution and strain engineering. By combining graphene with dissipation dilution and strain engineering in phononic crystals (PnCs), we propose PnC mechanical resonators possessing ultrahigh $Q$ and frequency simultaneously. Owing to the substantial prestress and the ultrahigh structural aspect ratio (feature size vs thickness) conferred by graphene, a tapered PnC resonator with the support of strain engineering breaks the upper limit of the theoretical $Q$ of soft clamping at room temperature. It benefits from the colocalization of the displacement and stress distribution of the resonant mode, enhancing $Q$ to $6.8\times {10}^8$ at 3.3 GHz. In addition, such 2D material PnC resonators can have efficient electrical tunability, including higher frequency and $Q$, via a simple gate setting. This innovative mechanical resonator holds promise for future phononic information processing, sensing, and quantum storage.

The results of polarization-dependent Raman spectroscopy of single-crystalline ${\mathrm{LiVO}}_2$ exhibiting transition to a diamagnetic state below $T_c\sim 500\mathrm{K}$ are reported. Our measurements clearly detect additional peaks in the low-temperature phase, which disappear nearly completely when heated above $T_c$. Proposed $\sqrt{3}\mathrm{a}\times \sqrt{3}\mathrm{a}$ lattice reconstruction explains these new Raman peaks by the Brillouin zone folding. The experiment, on the one hand, confirms that the symmetry of the nonmagnetic phase is not lower than trigonal, but, on the other hand, our thermal cycling study suggests possible stacking faults. This agrees with results of the density functional theory calculations, which show that the energy difference between different types of stacking does not exceed 1K per formula unit.