The appearance of an incommensurate charge density wave vector $\mathbf{Q}=(Q_x,Q_y)$ on multiband intermetallic systems presenting commensurate charge density wave (CDW) and superconductivity (SC) orders is investigated. We consider a two-band model in a square lattice, where the bands have distinct effective masses. The incommensurate CDW (inCDW) and CDW phases arise from an interband Coulomb repulsive interaction, while the SC emerges due to a local intraband attractive interaction. For simplicity, all the interactions, the order parameters, and hybridization between bands are considered $\mathbf{k}$ independent. The multiband systems that we are interested are intermetallic systems with a $d$ band coexisting with a large $c$ band, for which a mean-field approach has proved suitable. We obtain the eigenvalues and eigenvectors of the Hamiltonian numerically and minimize the free energy density with respect to the diverse parameters of the model by means of the Hellmann-Feynman theorem. We investigate the system in real as well as momentum space, and we find an inCDW phase with wave vector $\mathbf{Q}=(\pi ,Q_y)=(Q_x,\pi )$. Our numerical results show that the arising of an inCDW state depends on parameters such as the magnitude of the inCDW and CDW interactions, band filling, hybridization, and the relative depth of the bands. In general, inCDW tends to emerge at low temperatures, away from half-filling. We also show that whether the CDW ordering is commensurate or incommensurate, large values of the relative depth between bands may suppress it. We discuss how each parameter of the model affects the emergence of an inCDW phase.

The PXP model hosts a special set of nonergodic states, referred to as quantum many-body scars. One of the consequences of quantum scarring is the periodic revival of the wave function fidelity. It has been reported that quantum fidelity revival occurs in the PXP model for certain product states, and periodic driving of the chemical potential can enhance the magnitude of quantum revival and can even change the frequencies of revival showing the subharmonic response. Although the effect of the periodic driving in the PXP model has been studied in the limit of certain perturbative regimes, the general mechanism of such enhanced revival and frequency change has been barely studied. In this paper, we investigate how periodic driving in the PXP model can systematically control the fidelity revival. Particularly, focusing on a product state called the Néel state, we analyze the condition of driving to enhance the magnitude of revival or change the frequencies of revival. To clarify the reason for such control, we consider the similarities between the PXP model and the free spin-$1/2$ model in graph theoretical analysis and show that the quantum fidelity feature in the PXP model is well explained by the free spin-$1/2$ model. In addition, under a certain limit of the driving parameters, an analytic approach to explain the main features of the fidelity revival is also applied. Our results give insight into the scarring nature of the periodically driven PXP model and pave the way to understand the (sub)harmonic responses in these models and controls thereof.

Two-dimensional coherent spectroscopy (2DCS) is a nonlinear spectroscopy technique capable of identifying whether apparent continua in linear response are made out of multiplets of sharp deconfined quasiparticles. This makes it a potent tool for experimental identification of fractionalized phases. Previous discussions have focused on limits where the quasiparticles in question are infinitely long lived. In this paper we discuss 2DCS in the regime where the fractionalized quasiparticles can themselves decay. We introduce a powerful path-integral-based approach, whereby the computation of nonlinear susceptibilities reduces to an efficient exercise in diagrammatic perturbation theory. We apply this method to compute the 2DCS response of the one-dimensional transverse field Ising model, in the presence of integrability-breaking perturbations. We discuss aspects of the self-energy of the fractionalized quasiparticles that may be extracted via 2DCS, such as the momentum-dependent decay rate.

In 2010, the quantum anomalous Hall effect (QAHE) in graphene was proposed in the presence of Rashba spin-orbit coupling and a ferromagnetic exchange field. After a decade of experimental exploration, the anomalous Hall conductance can only reach about 0.25 in units of $2e^2/h$, which was attributed to the tiny Rashba spin-orbit coupling. Here, we show theoretically that Re-intercalation in a $\text{graphene}/{\mathrm{CrI}}_3$ heterostructure can not only induce sizable Rashba spin-orbit coupling ($>40$ meV), but also open up large band gaps at valleys $K$ (22.2 meV) and $K^{\prime }$ (30.3 meV), and a global band gap over 5.5 meV (19.5 meV with random Re distribution) hosting QAHE. A low-energy continuum model is constructed to explain the underlying physical mechanism. We find that Rashba spin-orbit coupling is robust against external stress whereas a tensile strain can increase the global bulk gap. Furthermore, we comprehensively explore the electronic properties of $3d, 4d, 5d$ transition-metal intercalation in graphene/${\mathrm{CrI}}_3$ systems.

Measurement-induced phase transitions (MIPTs) have attracted increasing attention due to the rich phenomenology of entanglement structures and their relation with quantum information processing. Since physical systems are unavoidably coupled to environment, quantum noise, which can qualitatively modify or even destroy certain entanglement structure, needs to be considered in analyzing a system with MIPT. In this Letter, we investigate the effect of quantum noise modeled by a reset quantum channel acting on each site with a probability $q$ on MIPT. Based on the numerical results from Clifford circuits, we show that the quantum noise can qualitatively change the entanglement properties—the entanglement obeys “area law” instead of “volume law” with a measurement rate $p<p_c$. In the noise-induced area law phase, the entanglement exhibits a novel $q^{-1/3}$ power-law scaling. Using an analytic mapping from the quantum model to a classical statistical model, we further show that the area law entanglement is the consequence of noise-driven symmetry-breaking field, and the $q^{-1/3}$ scaling can be understood as the result of Kardar-Parisi-Zhang fluctuations of directed polymer with an effective length scale $L_{\mathrm{eff}}\sim q^{-1}$ in a random environment.

We introduce a quantum error mitigation technique based on probabilistic error cancellation to eliminate errors which have accumulated during the application of a quantum circuit. Our approach is based on applying an optimal “denoiser” after the action of a noisy circuit and can be performed with an arbitrary number of extra gates. The denoiser is given by an ensemble of circuits distributed with a quasiprobability distribution. For a simple noise model, we show that efficient, local denoisers can be found and we demonstrate their effectiveness for the digital quantum simulation of the time evolution of simple spin chains.

Quasihole excitations in fractional quantum Hall (FQH) systems exhibit fractional statistics and fractional spin, but how the spin-statistics relation emerges from many-body physics remains poorly understood. Here we prove a spin-statistics relation using only FQH wave functions, on both the sphere and disk geometry. In particular, the proof on the disk generalizes to all quasiholes in realistic systems, which have a finite size and could be deformed into arbitrary shapes. Different components of the quasihole spins are linked to different conformal Hilbert spaces (CHSs), which are null spaces of model Hamiltonians that host the respective FQH ground states and quasihole states. Understanding how the intrinsic spin of the quasiholes is linked to different CHSs is crucial for the generalized spin-statistics relation that takes into account the effect of metric deformation. In terms of the experimental relevance, this enables us to study the effect of deformation and disorder that introduces an additional source of Berry curvature, an aspect of anyon braiding that has been largely neglected in previous literature.

We study the phase diagram of the spin-1 antiferromagnetic Heisenberg chain with uniaxial anisotropy and applied magnetic field in terms of the genuine multipartite entanglement as witnessed by the mean quantum Fisher information density. By considering the manifold generated by the staggered magnetization operator, we connect the state space curvature in the vicinity of the ground state of the Heisenberg chain to the genuine multipartite entanglement. Our analysis demonstrates that the quantum critical points and symmetry protected topological (SPT) phase exhibit large state space curvature, while the separable phases are completely flat, offering insight into the physical interpretation of state space curvature. We further show that the entanglement in the SPT phase is enhanced by the presence of uniaxial anisotropy and undiminished in the presence of uniform magnetic fields. The magnon condensate phase induced by large fields is shown to emanate from the Gaussian critical point and exhibits massive multipartite entanglement over a robust region of the parameter space.

We present a mechanism allowing for superconductivity at high magnetic fields, beyond the Pauli-Chandrasekhar-Clogston limit. We consider spin splitting induced by an in-plane external magnetic field in a superconductor with two relevant bands close to the Fermi level. The magnetic field therefore controls which bands are available for Cooper pair formation. The presence of interband superconducting pairing, i.e., Cooper pairs formed by electrons with different band indices, produces high-field reentrant superconducting domains, whose critical magnetic field violates the Pauli-Chandrasekhar-Clogston limit. We analyze how the interband superconducting domains are influenced by the band parameters, and show that, for a certain range of parameters, the system presents two separate superconducting regions, for low and high magnetic field.

Valence-skipped superconductors are natural candidates for unconventional superconductivity because they can exhibit a negative effective, attractive interaction for electron pairing. This work reports comprehensive x-ray diffraction, magnetization, specific heat, and muon spin rotation and relaxation measurements ($\mu \mathrm{SR}$) on the valence-skipped compound ${\mathrm{AgSnSe}}_2$. The temperature dependences of the electronic specific heat $\left[C_{\mathrm{el}}\left(T\right)\right]$ and the upper critical field $\left[H_{c2}\left(T\right)\right]$ provide evidence of two-gap superconductivity, which is also confirmed by our transverse-field $\mu \mathrm{SR}$ measurements. Zero-field $\mu \mathrm{SR}$ measurements reveal at most a slight increase $[\sim 0.002\left(1\right)\mu {\text{s}}^{-1}]$ in relaxation in the superconducting state, much less than reported in a range of superconductors with broken time-reversal symmetry. Further measurements with greatly improved statistics will be required to make a definitive determination of the possible presence of broken time-reversal symmetry.

We study the one-dimensional Hubbard model for two-component fermions with infinitely strong on-site repulsion ($t-0$ model) in the presence of disorder. Our analytical treatment demonstrates that the type of disorder drastically changes the nature of the emerging phases. The case of spin-independent disorder can be treated as a single-particle problem with Anderson localization. On the contrary, recent numerical findings show that spin-dependent disorder, which can be realized as a random magnetic field, leads to the many-body localization-delocalization transition. We find an explicit analytic expression for the matrix elements of the random magnetic field between the eigenstates of the $t-0$ model with potential disorder on a finite lattice. Analysis of the matrix elements supports the existence of the many-body localization-delocalization transition in this system and provides an extended physical picture of the random magnetic field.

Electric field control of magnetism using ferroelectric materials offers promising applications in low-power spintronics. We have conducted systematic density functional theory calculations to investigate the magnetic properties of epitaxial $5d$ transition metal monolayers on a ferroelectric substrate: $\mathrm{PbTi}{\mathrm{O}}_3$ (PTO). Our study reveals that the magnetocrystalline anisotropy energy of the osmium monolayer is significantly enhanced to 18.1 meV/Os in the upward polarization state and, moreover, the anomalous Hall coefficient of osmium/PTO film is tunable by reversing the electric polarization of the PTO substrate. Additionally, the electric polarization reversal in PTO rotates the easy magnetization axis of the iridium and platinum monolayers by ${90}^{\circ }$, which is attributed to the rearrangement of interfacial charges. Our findings suggest an efficient approach to control the magnetization direction of monoatomic layers and provide valuable insights for the development of low-energy spintronics devices.

We develop a microscopic theory of tunneling spin transport at the magnetic interface between a ferromagnetic insulator (FI) and a ferromagnetic superconductor (FSC) driven by ferromagnetic resonance. We show that the spin susceptibilities of the FSC can be extracted from the spin currents by tuning the easy axis of the FI, and thus the spin currents can be a probe for the symmetries of the spin-triplet Cooper pairing. Our results will offer a route to exploiting the synergy of magnetism and superconductivities for spin devices.

We propose theoretically a Josephson diode consisting of the conventional superconductors with the plain $s$-wave pairing and a chiral quantum dot. When an external magnetic field is exerted on the quantum dot, the critical current of the Josephson structure is different for the opposite directions of current flow. The strong nonreciprocity can be obtained in a large area of the parameter space. The inversion and the on/off state of the nonreciprocity can be conveniently regulated by adjusting the direction of the external field. The dependencies of the nonreciprocal behaviors on the hopping amplitude, the magnitude of the magnetic field, and the energy level of the quantum dot are investigated in details using the Keldysh nonequilibrium Green's function formalism under the self-consistent procedure. The symmetric and the antisymmetric properties of the nonreciprocity are analyzed from symmetries satisfied by the superconductors. The proposed diode effect also applies to other chiral conductors as interlayer. Its formation has no restriction on the type of the current-phase difference relations. The generality and flexibility of our proposed diode effect provides more possibilities for the design of the dissipationless diode devices.

Motivated by recent observations of threefold rotational symmetry breaking in twisted moiré systems, cold-atom optical lattices, quantum Hall systems, and triangular antiferromagnets, we phenomenologically investigate the strain-temperature phase diagram of the electronic 3-state Potts-nematic order. While in the absence of strain the quantum Potts-nematic transition is first order, quantum critical points (QCP) emerge when uniaxial strain is applied, whose nature depends on whether the strain is compressive or tensile. In one case, the nematic amplitude jumps between two nonzero values while the nematic director remains pinned, leading to a symmetry-preserving metanematic transition that terminates at a quantum critical end point. For the other type of strain, the nematic director unlocks from the strain direction and spontaneously breaks an in-plane twofold rotational symmetry, which in twisted moiré superlattices triggers an electric polarization. Such a piezoelectric transition changes from first to second order upon increasing strain, resulting in a quantum tricritical point. Using a Hertz-Millis approach, we show that these QCPs share interesting similarities with the widely studied Ising-nematic QCP. The existence of three minima in the nematic action also leaves fingerprints in the strain-nematic hysteresis curves, which display multiple loops. At nonzero temperatures, because the upper critical dimension of the 3-state Potts model is smaller than three, the Potts-nematic transition is expected to remain first order in three dimensions, but to change to second order in two dimensions (2D). As a result, the 2D strain-temperature phase diagram displays two first-order transition wings bounded by lines of critical end points or tricritical points, reminiscent of the phase diagram of metallic ferromagnets. We discuss how our results can be used to unambiguously identify spontaneous Potts-nematic order.

We derive and discuss the optical conductivity of $\alpha -{\mathcal{T}}_3$ materials with a finite band gap in their energy dispersions. In contrast with familiar $\alpha -{\mathcal{T}}_3$ materials, this constitutes a nontrivial case since the flat band changes into a curved one and two other branch dispersion relations become nonlinear beyond the limiting cases for graphene and the dice lattice. Such a unique band structure appears if the $\alpha -{\mathcal{T}}_3$ material is irradiated by a circularly polarized light nonresonantly. For this system, we have obtained optical conductivities at either zero or finite temperatures with nonzero or near-zero doping. Additionally, we demonstrate that analytical expressions can be obtained for all types of gapped $\alpha -{\mathcal{T}}_3$ materials, and, meanwhile, provide closed-form analytical expressions for a gapped dice lattice. Our current paper reproduces known properties of optical conductivity in unirradiated $\alpha -{\mathcal{T}}_3$ materials and silicene with two nonequivalent band gaps and, furthermore, demonstrates some very interesting irradiation-enabled behaviors which are absent in any Dirac materials. The discovery of unusual properties for the optical conductivity of gapped $\alpha -{\mathcal{T}}_3$ in this paper is expected to have many promising device applications, such as photodetectors, optical modulators, and metasurfaces.

The properties of two-dimensional (2D) electronic systems are often effectively controlled using electrostatic gating. The geometry of such field effect devices influences the effectiveness of the gate and the carrier density profile in the 2D device. Here, we analyze the gate-induced spatial variations in the lateral carrier density in patterned ${\mathrm{LaAlO}}_3/{\mathrm{SrTiO}}_3$ devices. We model the electrostatics of the 2D interface using the Thomas-Fermi approximation and compute the gate-induced charge distribution at the interface. We show that the electric field lines generated by the gate are focused at the edges of the device, causing an increased depletion near its edges. This effect is accentuated in ${\mathrm{LaAlO}}_3/{\mathrm{SrTiO}}_3$ due to the large, nonlinear dielectric constant of the substrate, and the large distance between the gate electrode and the interface. We experimentally demonstrate one consequence of this effect by directly imaging current distributions in gated heterostructures, finding that insulating regions nucleate at the edges of the device due to the gate. Our results suggest that device geometry and choice of dielectric materials control the charge distribution in 2D systems.

For a two-dimensional Hubbard model with spin-orbit Rashba coupling in external magnetic field the structure of effective spin interactions is studied in the regime of strong electron correlations and at half-filling. It is shown that in the third order of perturbation theory, the scalar and vector chiral spin-spin interactions of the same order arise. The emergence of the latter is due to orbital effects of magnetic field. It is shown that for nonuniform fields, scalar chiral interaction can lead to stabilization of axially symmetric skyrmion states with arbitrary topological charges. Taking into account the hierarchy of effective spin interactions, an analytical theory on the optimal sizes of such states, the higher-order magnetic skyrmions, is developed for axially symmetric magnetic fields of the form $h\left(r\right)\sim r^{\beta }$ with $\beta \in \mathbb{R}$.

We incorporate the microscopic assumptions that lead to a certain generalization of the Lieb-Schultz-Mattis (LSM) theorem for one-dimensional spin chains into the conformal bootstrap. Our approach accounts for the “LSM anomaly” possessed by these spin chains through a combination of modular bootstrap and correlator bootstrap of symmetry defect operators. Specifically, we obtain universal bounds on the local operator content of $(1+1)d$ conformal field theories (CFTs) that could describe translationally invariant lattice Hamiltonians with a ${\mathbb{Z}}_N\times {\mathbb{Z}}_N$ symmetry realized projectively at each site. We assume, for such models, that in the CFT the lattice translation symmetry is realized as an emanant internal ${\mathbb{Z}}_N$ symmetry. We present bounds on local operators both with and without refinement by their global symmetry representations. Interestingly, we can obtain nontrivial bounds on charged operators when $N$ is odd, which turns out to be impossible with modular bootstrap alone. Our bounds exhibit distinctive kinks, some of which are approximately saturated by known theories and others that are unexplained. We discuss additional scenarios with the properties necessary for our bounds to apply, including certain multicritical points between $(1+1)d$ symmetry protected topological phases, where we argue that the anomaly studied in our bootstrap calculations should emerge.

The anomalous Hall Effect (AHE) is one of the most fundamental phenomena related to band topology and holds great potential for technological applications. A promising approach to search for large AHE is to begin with a magnetic Weyl semimetal (WSM) and manipulate the Weyl nodes in the momentum-energy $\left(k-E\right)$ space. However, controlling the Weyl points is generally difficult because Weyl nodes can robustly exist at a generic momentum. Here we realize this approach in an experimentally confirmed ferromagnetic WSM ${\mathrm{Co}}_3{\mathrm{Sn}}_2{\mathrm{S}}_2$ via tension. Our calculations systematically demonstrate that the tension applied to ${\mathrm{Co}}_3{\mathrm{Sn}}_2{\mathrm{S}}_2$ can drive the movement and annihilation of Weyl nodes in the $k-E$ space, triggering a high-Chern-number three-dimensional quantum AHE topological phase transition and thus greatly boosting the AHE. We also found a rare way of annihilation of Weyl nodes occurring near the Brillouin zone boundary. Our work offers a promising way to boost the AHE and sheds light on the search for three-dimensional quantum anomalous Hall insulators.