We study the effect of spatially correlated classical noise on both Anderson and many-body localization of a disordered fermionic chain. By analyzing the evolution of the particle density imbalance following a quench from an initial charge density wave state, we find prominent signatures of localization also in the presence of the time-dependent noise, even though the system eventually relaxes to the infinite temperature state. In particular, for sufficiently strong static disorder, we observe the onset of metastability, which becomes more prominent the stronger the spatial correlations of the noise. In this regime, we find that the imbalance decays as a stretched-exponential—a behavior characteristic of glassy systems. We identify a simple scaling behavior of the relevant relaxation times in terms of the static disorder and of the noise correlation length. We discuss how our results could be exploited to extract information about the localization length in experimental setups.

Strongly interacting quantum systems subject to quenched disorder exhibit intriguing phenomena such as glassiness and many-body localization. Theoretical studies have mainly focused on disorder in the form of random potentials, while many experimental realizations naturally feature disorder in the interparticle interactions. Inspired by cold Rydberg gases, where such disorder can be engineered using the dipole blockade effect, we study a Heisenberg XXZ spin model where the disorder is exclusively due to random spin-spin couplings, arising from power-law interactions between randomly positioned spins. Using established spectral and eigenstate properties and entanglement entropy, we show that this system exhibits a localization crossover and identify strongly interacting pairs as emergent local conserved quantities in the system, leading to an intuitive physical picture consistent with our numerical results.

We study nonhomogeneous quantum quenches in a one-dimensional gas of repulsive spin-$1/2$ fermions, as described by the integrable Yang-Gaudin model. By means of generalized hydrodynamics (GHD), we analyze in detail the real-time evolution following a sudden change of the confining potential. We consider in particular release protocols and trap quenches, including a version of the quantum Newton's cradle. At zero temperature, we employ a simplified phase-space hydrodynamic picture to characterize the dynamics of the particle- and spin-density profiles. Away from zero temperatures, we perform a thorough numerical study of the GHD equations, and provide quantitative predictions for different values of the temperature, external magnetic field, and chemical potential. We highlight the qualitative features arising due to the multicomponent nature of the elementary excitations, discussing in particular effects of spin-charge separation and dynamical polarization.

We theoretically study the tunnel magnetoresistance (TMR) effect in (111)-oriented magnetic tunnel junctions (MTJs) with ${\mathrm{SrTiO}}_3$ barriers, $\mathrm{Co}/{\mathrm{SrTiO}}_3/\mathrm{Co}\left(111\right)$ and $\mathrm{Ni}/{\mathrm{SrTiO}}_3/\mathrm{Ni}\left(111\right)$. Our analysis combining the first-principles calculation and the Landauer formula shows that the Co-based MTJ has a high TMR ratio over 500%, while the Ni-based MTJ has a smaller value (290%). Since the in-plane lattice periodicity of ${\mathrm{SrTiO}}_3$ is about twice that of the primitive cell of fcc Co (Ni), the original bands of Co (Ni) are folded in the $k_x\text{−}{k}_y$ plane corresponding to the $ab$ plane of the MTJ supercell. We find that this band folding gives a half-metallic band structure in the ${\mathrm{\Lambda }}_1$ state of Co (Ni) and the coherent tunneling of such a half-metallic ${\mathrm{\Lambda }}_1$ state yields a high TMR ratio. We also reveal that the difference in the TMR ratio between the Co- and Ni-based MTJs can be understood by different $s$-orbital weights in the ${\mathrm{\Lambda }}_1$ band at the Fermi level.

A B-site disordered double perovskite $\mathrm{NdSrCoFe}{\mathrm{O}}_6$ was successfully synthesized by the conventional sol-gel method. Detailed experimental analyses revealed that $\mathrm{NdSrCoFe}{\mathrm{O}}_6$ crystallizes in the orthorhombic $Pnma$ space group, in which ${\mathrm{Co}}^{2+/3+}$ and ${\mathrm{Fe}}^{3+/4+}$ ions are randomly distributed at the BB′ sites, and ${\mathrm{Sr}}^{2+}$ and ${\mathrm{Nd}}^{3+}$ ions are respectively ordered at the A and A′ sites in an alternating arrangement along the $c$ direction. $\mathrm{NdSrCoFe}{\mathrm{O}}_6$ has a semimetallic-to-semiconducting transition nature, and a paramagnetic-ferromagnetic (FM) second-order phase transition originating from the complex hybridization between Co $3d$ and O $2p$ states is also found to occur at $T_{\mathrm{C}}\approx 150$ K. Then the spin coupling between ${\mathrm{Fe}}^{4+}\leftrightarrow {\mathrm{Co}}^{3+}$ and ${\mathrm{Fe}}^{3+}\leftrightarrow {\mathrm{Co}}^{2+}$ randomly distributed on the B and B′ sites leads to a FM cluster spin-glass behavior with characteristic parameters of $k=0.01, T_{\mathrm{SG}}=82.7$ K, $zv=1.89$, and ${\tau }_0=0.46\times {10}^{-4}$ s. Additionally, Griffiths-like phase behavior was observed in the region $T_{\mathrm{C}}<T<T_{\mathrm{GP}}$, with $T_{\mathrm{GP}}=245$ K, consistent with the power law exponent of $\lambda =0.74$. The maximum isothermal magnetic entropy change $-\mathrm{\Delta }{S}_M^{\max }\approx 1.84\mathrm{J}\mathrm{k}{\mathrm{g}}^{-1}{\mathrm{K}}^{-1}$ and relative cooling power $\approx 43.8\mathrm{J}\mathrm{k}{\mathrm{g}}^{-1}$ under a field of 40 kOe also indicate a magnetocaloric coupling wherein fitted critical exponents $\beta =1.384, \gamma =0.621$, and $\delta =1.421$ are far from any conventional universality class. Density functional theory calculations demonstrated spin short- and long-range ordering competitions for Fe/Co at BB′ sites, which arise predominantly from the stronger negatively charged ligand interaction with Co $3d$ orbitals and the weakest Fe $3d$ orbitals. This unconventional behavior is expected to be the main reason for the experimentally observed magnetic exchange distance decreasing with $J\left(r\right)\approx r^{-4.7}$.

We fabricated an asymmetric nanoscale SQUID consisting of one nanobridge weak link and one Dayem bridge weak link. The current phase relation of these particular weak links is characterized by multivaluedness and linearity. While the latter is responsible for a particular magnetic field dependence of the critical current (so-called vorticity diamonds), the former enables the possibility of different vorticity states (phase winding numbers) existing at one magnetic field value. In experiments the observed critical current value is stochastic in nature, does not necessarily coincide with the current associated with the lowest energy state and critically depends on the measurement conditions. In this paper, we unravel the origin of the observed metastability as a result of the phase dynamics happening during the freezing process and while sweeping the current. Moreover, we employ special measurement protocols to prepare the desired vorticity state and identify the (hidden) phase slip dynamics ruling the detected state of these nanodevices. In order to gain insights into the dynamics of the condensate and, more specifically the hidden phase slips, we performed time-dependent Ginzburg-Landau simulations.

The quest to govern the driving forces behind superconductivity and gain control over the superconducting transition temperature $T_{\mathrm{c}}$ is as old as the phenomenon itself. Microscopically, this requires a proper understanding of the evolution of electron-lattice interactions in their parameter space. We report such a controlled study on $T_{\mathrm{c}}$ in ${\mathrm{In}}_x\mathrm{Te}$ via fine-tuning the In stoichiometry $x$. We find that increasing $x$ from 0.84 to 1 results in an enhancement of $T_{\mathrm{c}}$ from 1.3 K to 3.5 K accompanied by an increase of the electron-phonon coupling constant from 0.45 to 0.63. Employing first-principles calculations, we show that this behavior is driven by two factors, each taking the dominant role depending on $x$. For $x\lesssim 0.92$, the major role is played by the density of electronic states at the Fermi level. Above $x\sim 0.92$, the change in the density of states flattens while the enhancement of $T_{\mathrm{c}}$ continues. We attribute this to a systematic softening of lattice vibrations, amplifying the electron-phonon coupling, and hence, $T_{\mathrm{c}}$.

We report experimental evidence of the formation of antiferromagnetic clusters well within cuprate superconductor ${\mathrm{La}}_{1.85}{\mathrm{Sr}}_{0.15}{\mathrm{CuO}}_4$ (LCu) in a composite made of LCu and ferromagnet ${\mathrm{La}}_{0.6}{\mathrm{Sr}}_{0.4}{\mathrm{CoO}}_3$ (LCo). It is found that the exchange field of LCo suppresses the dynamic antiferromagnetic spin fluctuation of LCu and short-range-ordered superparamagnetic type antiferromagnetic (AFM) clusters are formed at the cost of superconducting volume fraction. With the help of linear and nonlinear ac-susceptibility measurements, we show evidence of thermal blocking of these antiferromagnetic clusters. Further, we show that the shrank superconducting volume fractions undergo the quantum size effect (QSE) and follow DeGennes-Tinkham theory on the finite size effect of a superconductor. These give a clear indication that the antiferromagnetic spin fluctuation can be a mediator of electron pairing in cuprate superconductors.

We study 1D quasilattices, especially self-similar ones that can be used to generate two-, three-, and higher dimensional quasicrystalline tessellations that have matching rules and invertible self-similar substitution rules (also known as inflation rules) analogous to the rules for generating Penrose tilings. The lattice positions can be expressed in a closed-form expression we call floor form: $x_n=S(n-\alpha )+(L-S)\lfloor \kappa (n-\beta )\rfloor$, where $L>S>0$ and $0<\kappa <1$ is an irrational number. We describe two equivalent geometric constructions of these quasilattices and show how they can be subdivided into various types of equivalence classes: (i) lattice equivalent, where any two quasilattices in the same lattice equivalence class may be derived from one another by a local decoration/gluing rule; (ii) self-similar, a proper subset of lattice equivalent where, in addition, the two quasilattices are locally isomorphic; and (iii) self-same, a proper subset of self-similar where, in addition, the two quasilattices are globally isomorphic (i.e., identical up to rescaling). For all three types of equivalence class, we obtain the explicit transformation law between the floor form expression for two quasilattices in the same class. We tabulate (in Table I and Fig. 5)the ten special self-similar 1D quasilattices relevant for constructing Ammann patterns and Penrose-like tilings in two dimensions and higher, and we explicitly construct and catalog the corresponding self-same quasilattices.

We identify a precise geometric relationship between (i) certain natural pairs of irreducible reflection groups (“Coxeter pairs”), (ii) self-similar quasicrystalline patterns formed by superposing sets of 1D quasiperiodically spaced lines, planes or hyperplanes (“Ammann patterns”), and (iii) the tilings dual to these patterns (“Penrose-like tilings”). We use this relationship to obtain all irreducible Ammann patterns and their dual Penrose-like tilings, along with their key properties in a simple, systematic and unified way, expanding the number of known examples from four to infinity. For each symmetry, we identify the minimal Ammann patterns (those composed of the fewest 1d quasiperiodic sets) and construct the associated Penrose-like tilings: 11 in 2D, 9 in 3D, and one in 4D. These include the original Penrose tiling, the four other previously known Penrose-like tilings, and sixteen that are new. We also complete the enumeration of the quasicrystallographic space groups corresponding to the irreducible noncrystallographic reflection groups, by showing that there is a unique such space group in 4D (with nothing beyond 4D).

$\mathrm{Pb}{\mathrm{Fe}}_{1/2}{\mathrm{Nb}}_{1/2}{\mathrm{O}}_3$ (PFN) is a relaxor ferroelectric ($T_c\sim 400\mathrm{K}$) consisting of magnetic ${\mathrm{Fe}}^{3+}$ ($S=\frac{5}{2}, L\approx 0$) ions disordered throughout the lattice and hosts a spin-glass phase at low temperatures built from spatially isolated clusters of ${\mathrm{Fe}}^{3+}$ ions, termed a “cluster glass” [Kleemann et al., Phys. Rev. Lett. 105, 257202 (2010)]. We apply neutron scattering to investigate the magnetism and dynamics of this phase in a large single crystal which displays a low-temperature spin-glass transition ($T_g\sim 15\mathrm{K}$, found with magnetization), but no observable macroscopic and spatially long-range antiferromagnetic order. The static response in the low-temperature cluster-glass phase (sampled on the timescale set by our resolution) is found to be characterized by an average magnetic spin direction that lacks any preferred direction. The dynamics that drive this phase are defined by a magnetic correlation length that gradually increases with decreasing temperature. However, below $\sim 50\mathrm{K}$ the opposite is found with spatial correlations gradually becoming more short ranged, indicative of increasing disorder on cooling, thereby unraveling magnetism, until the low-temperature glass phase sets in at $T_g\sim 15\mathrm{K}$. Neutron spectroscopy is used to characterize the spin fluctuations in the cluster-glass phase and are found to be defined by a broadband of frequencies on the scale of terahertz, termed here “fast” fluctuations. The frequency bandwidth driving the magnetic fluctuations mimics the correlation length and decreases until $\sim 50\mathrm{K}$, and then increases again until the glass transition. Through investigating the low-energy acoustic phonons we find evidence of multiple distinct structural regions which form the basis of the clusters, generating a significant amount of local disorder. We suggest that random molecular fields originating from conflicting interactions between clusters is important for the destruction of magnetic order and the eventual formation of the cluster glass in PFN.

The correspondence between the real-complex transition in energy and delocalization-localization transition is well established in a class of Aubry-André-Harper model with exponential non-Hermitian on-site potentials. In this paper, we study a generalized Aubry-André model with off-diagonal modulation and non-Hermitian on-site potential. We find that, when there exists an incommensurate off-diagonal modulation, the correspondence breaks down, although the extended phase is maintained in a wide parameter range of the strengths of the on-site potential and the off-diagonal hoppings. An additional intermediate phase with a non-Hermitian mobility edge emerges when the off-diagonal hoppings become commensurate. This phase is characterized by the real and complex sections of the energy spectrum corresponding to the extended and localized states. In this case, the aforementioned correspondence reappears due to the recovery of the $\mathcal{PT}$ symmetry.

We employ unsupervised learning tools to identify the dynamical phases and their measurement-induced transitions in quantum systems subject to the combined action of unitary evolution and stochastic local measurements. Specifically, we show that the principal component analysis and the intrinsic dimension estimation provide order parameters that directly locate the transition and the critical exponents in the classical encoding data space. Finally, we test our approach on stabilizer circuits as proof of principle, finding robust agreement with previous studies.

Quantum phase transitions in quantum magnets constitute an important field that has attracted great interests. Although a variety of analytic and numerical methods have been introduced in this direction, faithful fermionic descriptions are still desired because they can transform the spin models to a form tractable by conventional many-body techniques, yielding more transparent physical pictures. We generalize the Chern-Simons fermionization approach and apply it to the XXZ quantum magnets. After fermionzation, the Ising interaction of the XXZ spin model leads to a fermion-fermion interaction. We show that the additional fermion-fermion interaction generates an interesting phase transition between two fermionic ordered states, i.e., the Chern-Simons superconductor and the Chern-Simons exciton insulator. We also demonstrate that this transition in the fermionic language essentially describes the quantum phase transition between the planar and out-of-plane Néel orders in the spin picture. The fermionic mean-field theory further leads to a nonlinear $\sigma$ model that describes the quantum phase transition, which is further supported by our density matrix renormalization group calculations in the original spin model. Our work introduces a fermionic interpretation of quantum phase transitions and advances the existing knowledge of quantum magnets.

In this paper, we present an in-depth analysis of the condensation energy $E_c$ for a superconductor in a situation when superconductivity emerges out of a non-Fermi liquid due to pairing mediated by a massless boson. This is the case for electronic-mediated pairing near a quantum-critical point in metal, for pairing in SYK-type models, and for phonon-mediated pairing in the properly defined limit, when the dressed Debye frequency vanishes. We consider a subset of these quantum-critical models, in which the pairing in a channel with a proper spatial symmetry is described by an effective $0+1$ dimensional model with the effective dynamical interaction $V\left({\mathrm{\Omega }}_m\right)={\overline{g}}^{\gamma }/{\left|{\mathrm{\Omega }}_m\right|}^{\gamma }$, where $\gamma$ is model-specific (the $\gamma$ model). In previous papers, we argued that the pairing in the $\gamma$ model is qualitatively different from that in a Fermi liquid, and the gap equation at $T=0$ has an infinite number of topologically distinct solutions, ${\mathrm{\Delta }}_n\left({\omega }_m\right)$, where an integer $n$, running between 0 and infinity, is the number of zeros of ${\mathrm{\Delta }}_n\left({\omega }_m\right)$ on the positive Matsubara axis. This gives rise to the set of extrema of $E_c$ at $E_{c,n}$, of which $E_{c,0}$ is the global minimum. The spectrum $E_{c,n}$ is discrete for a generic $\gamma <2$ but becomes continuous at $\gamma =2–0$. Here, we discuss in more detail the profile of the condensation energy near each $E_{c,n}$ and the transformation from a discrete to a continuous spectrum at $\gamma \to 2$. We also discuss the free energy and the specific heat of the $\gamma$ model in the normal state.

We discuss pairing of excitons and polaritons under effective spin-orbit coupling in two-dimensional semiconductors. The spin-orbit coupling is shown to induce dynamical broadening of a two-body bound state. Application of a transverse magnetic field yields the rich Feshbach resonance phenomenology. We predict quantum bosonic halos with a synthetic angular momentum $L_z=\pm 2\hslash$. The $d$-wave-like dressing of the nominally $s$-wave bound state is induced by spin-orbital coupling to the continuum in the open channel. As a possible manifestation of the phenomenon in the equilibrium phase diagram we predict biexcitonic Mott supercurrent: Dissociation of a biexciton Bose-Einstein condensate into a superfluid current of excitons upon increasing the density.