We characterize topological features of Josephson junctions formed by coupled mesoscopic chiral $p$-wave superconducting islands. Through analytic and numerical studies of the low-lying BdG (Bogoliubov-deGennes) spectrum, we identify localized MBS (Majorana bound states) nucleated in Josephson vortices by the application of a perpendicular magnetic field. Additionally, we demonstrate the existence of an extended MBS that is delocalized around the outer perimeter of the coupled islands, which has measurable consequences on the Josephson supercurrent and phase dynamics of the junction. In particular, we predict a change in the critical current diffraction pattern in which the odd integer-flux nodes are lifted in a fermion parity-dependent fashion. We model the competing stochastic effects of thermal noise and macroscopic quantum tunneling within the RCSJ framework and show the emergence of a bimodal critical current distribution. We demonstrate that increasing the parity transition rate suppresses the bimodal nature of the distribution, thus strongly emphasizing the nontrivial parity dependent nature of the many-body ground state. Finally, we consider a trijunction geometry with three islands and discuss possible schemes to braid Majorana bound states by moving the Josephson vortices to which they are bound.

We propose to exploit currently available tunnel ferromagnetic Josephson junctions to realize a hybrid superconducting qubit. We show that the characteristic hysteretic behavior of the ferromagnetic barrier provides an alternative and intrinsically digital tuning of the qubit frequency by means of magnetic field pulses. To illustrate functionalities and limitation of the device, we discuss the coupling to a readout resonator and the effect of magnetic fluctuations. The possibility to use the qubit as a noise detector and its relevance to investigate the subtle interplay of magnetism and superconductivity is envisaged.

We present a generic mechanism that explains why many Kondo materials show magnetic ordering along directions that are not favored by the crystal-field anisotropy. Using a renormalization-group (RG) analysis of single-impurity Kondo models with single-ion anisotropy, we demonstrate that strong fluctuations above the Kondo temperature drive a moment reorientation over a wide range of parameters, e.g., for different spin values $S$ and number of Kondo channels $N$. In tetragonal systems, this can happen for both easy-plane or easy-axis anisotropy. The characteristic crossing of magnetic susceptibilities is not an artifact of the weak-coupling RG treatment but can be reproduced in brute-force perturbation theory. Employing the numerical renormalization group (NRG), we show that for an underscreened moment $(S=1,$ $N=1)$ with easy-plane anisotropy, a crossing of magnetic susceptibilities can also occur in the strong-coupling regime (below the Kondo temperature). This suggests that collective magnetic ordering of such underscreened moments would develop along the magnetic hard axis.

We present a study of the control of electric field induced strain on the magnetic and electrical transport properties in a magnetoelastically coupled artificial multiferroic ${\mathrm{Fe}}_3{\mathrm{O}}_4/{\mathrm{BaTiO}}_3$ heterostructure. In this ${\mathrm{Fe}}_3{\mathrm{O}}_4/{\mathrm{BaTiO}}_3$ heterostructure, the ${\mathrm{Fe}}_3{\mathrm{O}}_4$ thin film is epitaxially grown in the form of bilateral domains, analogous to a-c stripe domains of the underlying ${\mathrm{BaTiO}}_3\left(001\right)$ substrate. By in situ electric field dependent magnetization measurements, we demonstrate the extrinsic control of the magnetic anisotropy and the characteristic Verwey metal-insulator transition of the epitaxial ${\mathrm{Fe}}_3{\mathrm{O}}_4$ thin film in a wide temperature range between 20–300 K, via strain mediated converse magnetoelectric coupling. In addition, we observe strain induced modulations in the magnetic and electrical transport properties of the ${\mathrm{Fe}}_3{\mathrm{O}}_4$ thin film across the thermally driven intrinsic ferroelectric and structural phase transitions of the ${\mathrm{BaTiO}}_3$ substrate. In situ electric field dependent Raman measurements reveal that the electric field does not significantly modify the antiphase boundary defects in the ${\mathrm{Fe}}_3{\mathrm{O}}_4$ thin film once it is thermodynamically stable after deposition and that the modification of the magnetic properties is mainly caused by strain induced lattice distortions and magnetic anisotropy. These results provide a framework to realize electrical control of the magnetization in a classical highly correlated transition metal oxide.

Level attraction is a type of mode hybridization in open systems where instead of forming a hybridization gap, the energy spectrum of two modes coalesce in a region bounded by exceptional points. We demonstrate that this phenomenon can be realized in a Floquet system with memory, which appears in describing linear excitations in a nonlinear driven system with a limit cycle. Linear response of the system in this state is different from its response near thermodynamic equilibrium. We develop a general formalism and provide an example in the context of cavity magnonics, where we show that magnetic excitations in systems driven far from the equilibrium may show level attraction with cavity photons. Our approach works equally well for quantum and semiclassical magnetic dynamics. The theory is formulated so it can be used in combination with micromagnetic simulations to explore a wide range of experimentally interesting systems.

Antiferromagnetic fluctuations in two dimensions cause a decrease in spectral weight at so-called hot spots associated with the pseudogap in electron-doped cuprates. In the $2\text{D}$ Hubbard model, these hot spots occur when the Vilk criterion is satisfied, namely, when the spin correlation length exceeds the thermal de Broglie wavelength. Using the two-particle self-consistent approach, here we show that this criterion may be violated near the antiferromagnetic quantum critical point when sufficient disorder is added to the model. Static disorder decreases inelastic scattering, in contradiction with Matthiessen's rule, leading to a shift in the position of the quantum critical point and a modification of the conditions for the appearance of hot spots. This opens the road to a study of the interplay between disorder, antiferromagnetic fluctuations, and superconductivity in electron-doped cuprates.

Systems containing the ideal kagome lattice can exhibit several distinct and novel exotic states of matter. One example of such systems is a recently discovered $A{\mathrm{V}}_3{\mathrm{Sb}}_5$ ($A=\mathrm{K}$, Rb, and Cs) family of compounds. Here the coexistence of the charge density wave (CDW) and superconductivity is observed. In this paper, we study the dynamic properties of the $A{\mathrm{V}}_3{\mathrm{Sb}}_5$ systems in context of origin of the CDW phase. We show and discuss the structural phase transition from $P6/mmm$ to $C2/m$ symmetry that is induced by the presence of phonon soft modes. We conclude that the CDW observed in this family of compounds is a consequence of the atom displacement, from the high-symmetry position of the kagome net, in the low-temperature phase. Additionally, using the numerical ab initio methods, we discuss the charge distribution on the $A{\mathrm{V}}_3{\mathrm{Sb}}_5$ surface. We show that the observed experimental stripelike modulation of the surface can be related to surface reconstruction and manifestation of the three-dimensional $2\times 2\times 2$ bulk CDW. Finally, the consequence of realization of the $C2/m$ structure on the electronic properties is discussed. We show that the electronic band structure reconstruction and the accompanying modification of density of states correspond well to the experimental data.

We theoretically analyze the Fano interference in a single impurity multi-Weyl semimetal hybrid system and show the emergence of the topological charge Fano effect in the bulk local density of states. In multi-Weyl semimetals, the number of Fermi arcs at the system boundaries is determined by the topological charge $J$, a direct consequence of the “bulk-boundary” correspondence principle. Analogously, we find that $J$ also modulates the bulk Fano profile of the system with an embedded quantum impurity. Thus by increasing $J$, the Fano line shape evolves from resonant, typical for $J=1$ (single Weyl), towards antiresonant, extrapolating to the so-called hyper Weyl semimetals with $J\gg 1$. Specially for the maximum case protected by the rotational symmetry $C_{2J=6}$, namely, the $J=3$ (triple Weyl), which acquires asymmetric Fano profile, the Fano parameter absolute value is predicted to be $tan\left(C_{2J=6}\right)$, where $C_{2J}\equiv ({360}^{\circ }/2J)$ defines the rotational angle. Hence, the Fano discretization in the $J$ term introduces the topological charge Fano effect in multi-Weyl semimetals. We also suggest a transport device where we expect that the proposed Fano effect could be detected.

Electronic and magnetic ordered states are strongly correlated to the dimensions of matter. Here we report a dimensional crossover in self-intercalated antiferromagnetic ${\mathrm{V}}_5{\mathrm{S}}_8$ nanoflakes. The transition of three-dimensional (3D) to two-dimensional (2D) transport, evidenced by thickness-independent conductivity, occurs when the thickness of ${\mathrm{V}}_5{\mathrm{S}}_8$ flakes is reduced to ∼7.3 nm. At low temperatures, 3D transport follows Fermi liquid behavior, but 2D transport suggests the emergence of Kondo physics with a logarithmic dependence on the temperature and a negative magnetoresistance of a 5.0 nm thick ${\mathrm{V}}_5{\mathrm{S}}_8$ flake at low temperatures for both in-plane and perpendicular magnetic fields. At temperatures higher than 6 K, the magnetoresistance is positive and parabolically dependent on the magnetic field, indicating suppression of the antiferromagnetic order. Based on a simple magnon gas model, a temperature-independent effective magnon moment $(\sim 1g{\mu }_B)$ is extracted from the Hall coefficient for all ${\mathrm{V}}_5{\mathrm{S}}_8$ flakes with different thicknesses. Our results reveal that dimensional crossover plays an important role in tuning the electronic properties in 2D metallic transition-metal dichalcogenides (TMDs).

Following the recent observation of wave function revivals in large Rydberg atom quantum simulators, much effort has focused on understanding the emergence of many-body scars in nonintegrable quantum systems. Here we explore the origin of scarred wave function revivals in a family of models obtained by deforming the graph adjacency matrix of the PXP model—the effective model of Rydberg atoms in the strong Rydberg blockade regime. We consider deformations that either enhance the Rydberg constraint, ultimately resulting in an effective tight-binding model of two hypercubes joined at a single vertex, or relax the constraint until reaching the free spin-1/2 model. In the former case, we argue that the model of two joined hypercubes captures the essential features of many-body scarring present in the PXP model. On the other hand, relaxing the constraint leads to a sequence of new scarred models, some with more robust scarring signatures than the PXP model, as can be understood from the graph-theoretic viewpoint. Our results shed light on the nature of scarring in the PXP model by identifying its simple parent model, while also highlighting its distinction from the free-spin precession.

Disordered quantum systems undergoing a many-body localization (MBL) transition fail to reach thermal equilibrium under their own dynamics. Distinguishing between asymptotically localized or delocalized dynamics based on numerical results is, however, nontrivial due to finite-size effects. Numerical linked cluster expansions (NLCE) provide a means to tackle quantum systems directly in the thermodynamic limit but are challenging for models without translational invariance. Here we demonstrate that NLCE provides a powerful tool to explore MBL by simulating quench dynamics in disordered spin-$1/2$ two-leg ladders and Fermi-Hubbard chains. Combining NLCE with an efficient real-time evolution of pure states, we obtain converged results for the decay of the imbalance on long time scales and show that, especially for intermediate disorder below the putative MBL transition, NLCE outperforms direct simulations of finite systems with open or periodic boundaries. Furthermore, while spin is delocalized even in strongly disordered Hubbard chains with frozen charge, we unveil that an additional tilted potential leads to a drastic slowdown of the spin imbalance and nonergodic behavior on accessible times. Our work sheds light on MBL in systems beyond the well-studied disordered Heisenberg chain and emphasizes the usefulness of NLCE for this purpose.

We present an experimental and theoretical study of dysprosium metal compressed in the soft pressure transmitting medium Ne up to 182 and 300 GPa, respectively. Angle-dispersive x-ray powder diffraction data from each of the high-pressure polymorphs shows anisotropic compression behavior indicating changes to the electron density distribution throughout its polymorphic landscape. We compare the monoclinic $\left(m\mathrm{C}4\right)$ and orthorhombic $\left(o\mathrm{F}16\right)$ structures for the collapsed structure for Dy above 82 GPa and verify that the $o\mathrm{F}16$ structure offers a better fit to our data than the previously reported $m\mathrm{C}4$ structure. Further, we have found that the $o\mathrm{F}16$ structure undergoes similar anisotropic compression of its lattice parameters, with a turning point above 160 GPa; suggesting a potential phase transition at pressures much higher than achieved in this study. Density functional theory calculations show the likely candidate for this new high-pressure phase is the isosymmetric $o\mathrm{F}8$ structure, which is predicted to be lower in energy than the $o\mathrm{F}16$ structure above 275 GPa.

We report a theoretical investigation on the effects of interface reconstruction on magnetic anisotropy (MA) and Dzyaloshinskii-Moriya interaction (DMI) for nonisostructural heterostructures formed by an infinite-layer oxide ${\mathrm{SrCuO}}_2$ and a perovskite oxide ${\mathrm{SrRuO}}_3$. Due to the atomic, charge, spin, and orbital reconstructions at interface, the SRO film thickness-dependent magnetic anisotropy oscillation behavior has been greatly tuned in two ${\mathrm{SrCuO}}_2/{\mathrm{SrRuO}}_3$ heterostructures. A strong DMI of 3.5 meV/Ru and a large DMI/exchange constant ratio $\left|D/J\right|$ of 0.63 are obtained at the ${\mathrm{CuO}}_2\text{−}\mathrm{Sr}\text{−}{\mathrm{RuO}}_2$ interface, which are beneficial to the creation and stability of skyrmions. Besides, the DMI is tunable, monotonically decreasing with the increase of the content of the apical oxygen ions in the interfacial layer, and takes the minimal value of 0.1 meV/Ru at the ${\mathrm{CuO}}_2\text{−}\mathrm{SrO}\text{−}{\mathrm{RuO}}_2$ interface. We evaluate the formation energy of oxygen vacancy in interface SRO layer, which turns out to be half as much as that in bulk SRO. This small value ensures the experimental feasibility towards two interfaces. Combining first-principles calculations with tight-binding model, we find that the effectively modulated MA and DMI at the ${\mathrm{CuO}}_2\text{−}\mathrm{Sr}\text{−}{\mathrm{RuO}}_2$ interface are mainly associated with the occupation of $d_{3z^2-r^2}$ orbital, the enhanced interface symmetry breaking, and orbital hybridization. The present work demonstrates the distinct features of the interface formed between nonisostructural oxides and suggests a conceptually different strategy towards the modulation of MA and DMI.

The entire magnetization process in the two-leg organic spin ladder BIP-TENO is studied with an ultrahigh magnetic field of up to 150 T. Nontrivial multiple magnetization plateaus are observed, indicating there exist strong quantum correlations between spins. In addition to the previously reported 1/4 plateau, another plateau appears at 1/3 magnetization only when spins are decoupled to the lattice degree of freedom in the adiabatic limit. Spontaneous symmetry breaking is expected to occur with the spin-lattice decoupling induced by a fast evolution of external magnetic fields in the range of $\mu$s. Under the adiabatic condition, five fractional (1/4, 1/3, 1/2, 2/3, and 3/4) magnetization plateaus are likely to appear with an assumption that the magnetization saturates at around 160 T.

The discovery of higher-temperature superconductivity in FeSe monolayers on ${\mathrm{SrTiO}}_3$ substrates has sparked a surge of interest in the interface superconductivity. One point of agreement reached to date is that modulation doping by impurities in the substrate is critical for the enhanced superconductivity. Remarkably, the universal doping about 0.1 electrons per Fe, i.e., so-called “magic” doping, has been observed on a range of Ti oxide substrates, which concludes that there likely is some important interaction limiting the FeSe doping. Our study discovers that the polarization change at the interface Se because of the close proximity to the substrate from that in the free-standing FeSe film significantly amplifies the total potential difference at the interface above and beyond the work function difference for charge transfer. Additionally, the titanate substrate with a large number of free electrons basically serves as an “infinite” charge reservoir, which leads to the saturated FeSe doping with the complete removal of the interface potential gradient. Our work has developed the theory for modulation doping in the van der Waals materials/oxides heterostructure, providing a solution to the puzzle of magic doping in FeSe monolayers on titanates. The information also presents experimental pathways to accommodate a variable carrier density of FeSe monolayers via modulation doping.

The $E3$ transition in irradiated GaAs observed in deep level transient spectroscopy (DLTS) was recently discovered in Laplace-DLTS to encompass three distinct components. The component designated $E3c$ was found to be metastable, reversibly bleached under minority carrier (hole) injection, with an introduction rate dependent upon Si doping density. It is shown through first-principles modeling that the $E3c$ must be the intimate Si-vacancy pair, best described as a Si sitting in a divacancy ${\mathrm{Si}}_{vv}$. The bleached metastable state is enabled by a doubly site-shifting mechanism: Upon recharging, the defect undergoes a second site shift rather returning to its original $E3c$-active configuration via reversing the first site shift. Identification of this defect offers insights into the short-time annealing kinetics in irradiated GaAs.

Engineering oxygen octahedra rotation patterns in $AB{\text{O}}_3$ perovskites is a powerful route to design functional materials. Here we propose a strategy that exploits point defects that create local electric dipoles and couple to the oxygen sublattice, enabling direct actuation on the rotational degrees of freedom. This approach, which relies on substituting an $A$ site with a smaller ion, paves a way to couple dynamically octahedra rotations to external electric fields. A common antisite defect, ${\mathrm{Al}}_{\mathrm{La}}$, in rhombohedral ${\mathrm{LaAlO}}_3$ is taken as a prototype to validate the idea, with atomistic density functional theory calculations supported with an effective lattice model to simulate the dynamics of switching of the local rotational degrees of freedom to long distances. Our simulations provide an insight of the main parameters that govern the operation of the proposed mechanism, and allow to define guidelines for screening other systems where this approach could be used for tuning the properties of the host material.

As one of the most striking phenomena in many-body systems, the breakdown of the adiabatic Born-Oppenheimer (ABO) approximation is essential for understanding and predicting the dynamics of quantum materials. Here, we demonstrate that strong nonadiabatic (NA) effects can emerge in electron-phonon coupling (EPC) and resultant superconductivity, yielding a surprisingly large contribution (up to 20%) to the total EPC strength λ of doped graphene/graphane and modulating the superconductivity transition temperature $T_c$ by ∼20%. The NA EPC, with a detectable isotopic effect, results from the renormalized EPC matrix elements (up to 40%) combined with the Fermi surface modulation, due to electron distributions deviating from the equilibrium. Our results imply that nonadiabaticity plays a wider and more important role than previously conceived, offering new understandings and strategies for dynamic engineering of quantum materials.