We study formation and screening of local magnetic moments in the two-band Hubbard model in the presence of Hund exchange interaction using dynamic mean-field theory approach. The characteristic temperatures of the formation, beginning and full screening of local magnetic moments are obtained from the analysis of temperature dependence of the orbital, charge, and spin susceptibilities, as well as the respective instantaneous correlation functions. At half filling we find the phase diagram, which is similar to the single-orbital case with wide region of formation of local magnetic moments below the orbital Kondo temperature. Similar to the single-orbital case, with decreasing temperature the screening of local magnetic moments is preceded by appearance of fermionic quasiparticles. In the two-band case the quasiparticles are however present also in some temperature region above the Mott insulating phase. At finite doping we find broad regime of presence of local magnetic moments, which coexist with incoherently or coherently moving holes. We also find, similar to the half-filled case, finite-temperature interval in the doped regime, when the fermionic quasiparticles are formed, but do not yet screen local magnetic moments.

Misfit layer compounds, heterostructures composed of a regular alternating stacking of rocksalt monochalcogenide bilayers and few-layer transition-metal dichalcogenides, are an emergent platform to investigate highly doped transition-metal dichalcogenides. Among them, (LaSe)${}_{1.14}{\left({\mathrm{NbSe}}_2\right)}_2$ displays Ising superconductivity, while the presence of a charge density wave (CDW) in the material is still under debate. Here, by using polarized Raman spectroscopy and first-principles calculations, we show that ${\mathrm{NbSe}}_2$ undergoes a doping-driven collapse of the CDW ordering within the misfit, and no signature of the CDW is detected down to 8 K. We provide a complete experimental and theoretical description of the lattice dynamics of this misfit compound. We show that the vibrational properties are obtained from those of the two subunits, namely, the LaSe unit and the ${\mathrm{NbSe}}_2$ bilayer, in the presence of a suitable field-effect doping, and then highlight the two-dimensional nature of the lattice dynamics of ${\mathrm{NbSe}}_2$ within the (LaSe)${}_{1.14}{\left({\mathrm{NbSe}}_2\right)}_2$ three-dimensional structure.

We present a broad study of charge and heat transport in a mesoscopic system where one or several quantum Hall edge channels are strongly coupled to a floating Ohmic contact (OC). It is well-known that charge-current fluctuations emanating from the OC along the edge channels are highly susceptible to the OC charge capacitance in the heat Coulomb blockade regime (an impeded ability of the OC to equilibrate edge channels). Here, we demonstrate how potential and temperature fluctuations due to finite OC charge and heat capacities impact the heat-current fluctuations emitted from the OC. First, by assuming an infinite OC heat capacity, we show that the output heat-current noise is strongly dependent on the OC charge capacitance, following from a close relation between one-dimensional charge and heat currents. When also the OC heat capacity is finite, an interplay of potential and temperature fluctuations influences the heat transport. Concretely, we find that the effect of the charge capacitance on heat transport manifests in terms of a strongly increased energy relaxation time in the heat Coulomb blockade regime. Furthermore, we find expressions for a broad set of output observables, such as charge and heat auto- and cross correlations, as functions of input and OC fluctuations, depending on the relation between charge and energy relaxation times compared to the frequency of fluctuations and inverse (local) temperatures as well as on the number of edge channels attached to the OC. Finally, we show that a finite OC heat capacity transforms the full counting statistics of the output charge from Gaussian to non-Gaussian. Our findings provide opportunities to experimentally probe and harness the quantum nature of heat transport in strongly coupled electron circuits.

The Coulomb impurity problem of graphene, in the absence of a magnetic field, displays discrete scale invariance. Applying a magnetic field introduces a new magnetic length scale $\ell$ and breaks discrete scale invariance. Moreover, a magnetic field is a singular perturbation as it turns complex energies into real energies. Nonetheless, the Coulomb potential must be regularized with a length $R$ at short distances for supercritical impurities. We investigate the structure of the induced density of a filled Landau impurity band in the supercritical regime. The coupling between Landau level states by the impurity potential is nontrivial and can lead to several anomalous effects. First, we find that the peak in the induced density can be located away from the center of the impurity, depending on the characteristics of the Landau impurity bands. Second, the impurity charge is screened, despite the Landau impurity band being filled. Third, anticrossing impurity states lead to additional impurity cyclotron resonances.

A different type of topological phase dubbed topological inverse Anderson insulators is proposed, which is characterized by the disorder-induced extended bulk states from the flat-band localization and topological edge states. Based on the topological invariant, the behaviors of the localization length of the zero-energy modes, and quantum transport, we identify its existence in several all-band-flat models with the disordered potentials or hopping including the $\pi$-flux Creutz ladder, the fully dimerized Su-Schrieffer-Heeger chain, and the $\pi$-flux diamond chain. Unlike the topological Anderson insulator, where disorder induces localization and exponential suppression of transport, the disorder-assisted quantum ballistic coherent transport can appear in the topological inverse Anderson insulator. In addition, our proposal and results could be realized by the current experimental techniques.

Quantum error correction (QEC) codes protect quantum information from errors due to decoherence. Many of them also serve as prototypical models for exotic topological quantum matters. Investigating the behavior of the QEC codes under decoherence sheds light on not only the codes' robustness against errors but also new out-of-equilibrium quantum phases driven by decoherence. The phase transitions, including the error threshold, of the decohered QEC codes can be probed by the systems' Rényi entropies $S_R$ with different Rényi indices $R$. In this paper, we study the general construction of the statistical models that characterize the Rényi entropies of QEC codes decohered by Pauli noise. We show that these statistical models can be organized into a “tapestry” woven by rich duality relations among them. For Calderbank-Shor-Steane (CSS) codes with bit-flip and phase-flip errors, we show that each Rényi entropy is captured by a pair of dual statistical models with randomness. For $R=2,3,\infty$, there are additional dualities that map between the two error types, relating the critical bit-flip and phase-flip error rates of the decoherence-induced phase transitions in the CSS codes. For CSS codes with an “$em$ symmetry” between the $X$-type and the $Z$-type stabilizers, the dualities with $R=2,3,\infty$ become self-dualities with super-universal self-dual error rates. These self-dualities strongly constrain the phase transitions of the code signaled by $S_{R=2,3,\infty }$. For general stabilizer codes decohered by generic Pauli noise, we also construct the statistical models that characterize the systems' entropies and obtain general duality relations between Pauli noise with different error rates.

We examine the existence and characteristics of the exotic Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) phase in a one-dimensional Fermi gas with attractive Hubbard interactions in the presence of spin-orbit coupling (SOC) and Zeeman field. We show that a robust FFLO phase can be created in the presence of attractive on-site interactions and Zeeman field, and that the addition of SOC suppresses the FFLO order and enhances the pair formation. In the absence of SOC, the system shows four phases: Bardeen-Cooper-Schrieffer (BCS), FFLO, multimode pairing, and fully polarized phases by tuning the Zeeman field $h$. The quantum transition between these phases is discontinuous with respect to $h$. In the presence of SOC, the transition from the BCS to FFLO phase becomes continuous. We present a complete phase diagram of this model both in the presence and in the absence of SOC at a quarter electron filling and also explore the effect of SOC on the FFLO phase.

Due to the large perpendicular magnetic anisotropy originating from spin-orbit coupling, magnetoelastic coupling is generally reported in easy-plane magnets with rectangular lattice where the easy axis is coupled with the lattice direction. Nevertheless, the acquisition of a coupling beyond the easy-plane ferromagnets in two-dimensional (2D) materials remains unknown. Here, by employing density functional theory calculations, we demonstrate this feasibility with the discovery of long-range ferromagnetic (FM) ordering and elastic strain-mediated chiral-like atomic distortion behavior in a newly tetragonal As-Fe-As trilayer (t-FeAs monolayer), which shows large perpendicular magnetic anisotropy, robust FM ordering, and in-plane ferroelasticity (FEL). We firstly point out that obvious limits exist when using the four magnetic configurations to determine the magnetic transition temperature for a rectangular spin lattice even if more exchange interaction parameters are included. A four-state mapping analysis is carefully examined for t-FeAs, where the calculated Curie temperature $T_{\mathrm{c}}$ is 435 K, which is higher than most reported 2D magnets and can be further tuned by appropriate strains. Intriguingly, the chiral-like atomic distortion behavior of the Fe sublayer is scanning-tunneling-microscopy characterizable, which can switch the magnetization axis between the out-of-plane and in-plane directions. This unusual finding of FEL manipulation of both the atomic displacement and spin properties makes t-FeAs a promising candidate for future spintronics and provides the possibility for exploring unprecedented coupling physics.

The memory effect in a single-crystal spin glass (${\mathrm{Cu}}_{0.92}{\mathrm{Mn}}_{0.08}$) has been measured using 1 Hz ac susceptibility techniques over a temperature range of $0.4–0.7T_g$, and a model of the memory effect has been developed. A double-waiting-time protocol is carried out where the spin glass is first allowed to age at a temperature below $T_g$, followed by a second aging at a lower temperature, $T_{w_2}$, after it has fully rejuvenated. The model is based on calculating typical coincident growth of correlated regions at the two temperatures. It accounts for the absolute magnitude of the memory effect as a function of both waiting times and temperatures. The data can be explained by the memory loss being a function of the relative change in the correlated volume at the first waiting temperature because of the growth in the correlations at the second waiting temperature.

The prototypical $\alpha \to \omega$ phase transition in zirconium is an ideal test bed for our understanding of polymorphism under extreme loading conditions. After half a century of study, a consensus had emerged that the transition is realized via one of two distinct displacive mechanisms, depending on the nature of the compression path. However, recent dynamic-compression experiments equipped with in situ diffraction diagnostics performed in the past few years have revealed new transition mechanisms, demonstrating that our understanding of the underlying atomistic dynamics and transition kinetics is in fact far from complete. We present classical molecular dynamics simulations of the $\alpha \to \omega$ phase transition in single-crystal zirconium shock compressed along the [0001] axis using a machine-learning-class potential. The transition is predicted to proceed primarily via a modified version of the two-stage Usikov-Zilberstein mechanism, whereby the high-pressure $\omega$ phase heterogeneously nucleates at boundaries between grains of an intermediate $\beta$ phase. We further observe the fomentation of atomistic disorder at the junctions between $\beta$ grains, leading to the formation of highly defective interstitial material between the $\omega$ grains. We directly compare synthetic x-ray diffraction patterns generated from our simulations with those obtained using femtosecond diffraction in recent dynamic-compression experiments, and show that the simulations produce the same unique, anisotropic diffuse scattering signal unlike any previously seen from an elemental metal. Our simulations suggest that the diffuse signal arises from a combination of thermal diffuse scattering, nanoparticlelike scattering from residual kinetically stabilized $\alpha$ and $\beta$ grains, and scattering from interstitial defective structures.

We present a Raman study of $\mathrm{ZrA}{\mathrm{s}}_2$ single crystals, a nodal-line semimetal with symmetry-enforced Dirac-like band crossings. We identified the symmetry of phonon modes by polarized light measurements and comparison with calculated phonon frequencies. Significant dependence of peak intensities on the excitation wavelength was observed, indicating quantum interference effects. Phonon peaks in the spectra were superimposed on the electronic background, with quasielastic scattering observed for the 785-nm excitation. The temperature dependence of phonon peaks’ linewidth indicates that the electron-phonon coupling plays an essential role in phonon decay.

We report the theoretical discovery of multiple real-space degenerate Floquet-Bloch states in monolayer graphene coherently driven by twisted circularly polarized light. Using Floquet theory, we characterize the real-space structure of quasienergies and Floquet modes in terms of the orbital angular momentum and radial vortex profile of light. We obtain the effective real-space Floquet Hamiltonian and show it supports crossings of Floquet modes, especially at high-symmetry $K$ and $\mathrm{\Gamma }$ points of graphene, localized at rings around the vortex center. At specific frequencies, the vortex bound states form a multiply degenerate structure in real space. This structure is purely dynamically generated and controlled by the frequency and tuned by the intensity of twisted light. We discuss the experimental feasibility of observing and employing multiple real-space degeneracies for coherent optoelectronic quantum state engineering.

We investigate the functionality of the $\mathrm{Cr}$-doped ${\mathrm{RuO}}_2$ as an electrode of the magnetic tunnel junction (MTJ), motivated by a recent experiment showing that $\mathrm{Cr}$ doping into rutile-type ${\mathrm{RuO}}_2$ is an effective tool to easily control its antiferromagnetic order and the resultant magnetotransport phenomena. We perform first-principles calculation of the tunnel magnetoresistance (TMR) effect in the MTJ based on the $\mathrm{Cr}$-doped ${\mathrm{RuO}}_2$ electrodes. We find that a finite TMR effect appears in the MTJ originating from the momentum-dependent spin splitting in the electrodes, which suggests that ${\mathrm{RuO}}_2$ with Cr doping will function effectively as the electrode of the MTJ. We also show that this TMR effect can be qualitatively captured by the local density of states inside the tunnel barrier.

Recently, the emergence of van Hove singularity, flat band, and Dirac cone in kagome materials has attracted tremendous interest as they are closely related to the superconductivity. Here, based on first-principles calculations, we propose these features can be realized in the topological pervoskites $A{\mathrm{CPd}}_3$ $(A=\text{Mg}, \mathrm{Ca}, \mathrm{Sr})$. In particular, the Dirac point is observed near the Fermi level with the spin-orbit coupling. The superconducting transition temperature $T_c$ is estimated to be 19.05, 15.37, and 10.25 K for ${\mathrm{MgCPd}}_3$, ${\mathrm{CaCPd}}_3$, and ${\mathrm{SrCPd}}_3$ by solving the Allen-Dynes modified McMillan formula, respectively. In general, the high $T_c$ can be attributed to the large electronic density of states near the Fermi level, which arises from the van Hove singularity and flat band. Noticeably, the declining trend of $T_c$ from ${\mathrm{MgCPd}}_3$ to ${\mathrm{SrCPd}}_3$ can be ascribed to the decreasing electron-phonon coupling that is related to the weakening of electron correlation. This point is further verified by doping holes (electrons) in ${\mathrm{CaCPd}}_3$, i.e., the $T_c$ would gradually increase to 18.41 K when the flat band gets more and more dispersionless. Thus these pervoskites provide solid platforms to explore the interplay among band topology, electron correlation and superconductivity.

This study revisits the electroabsorption (EA) spectrum of polyacetylene, ${\left(\mathrm{CH}\right)}_{\mathrm{x}}$ thin films, for both the cis- and trans-isomers, as functions of the electric field strength, isomerization degree, and light polarization states. The EA spectrum of cis-${\left(\mathrm{CH}\right)}_{\mathrm{x}}$ reveals an oscillatory feature that follows the Stark shift-related first derivative of the material's absorption spectrum that contains $v$(0-1) and $v$(0-2) sidebands of the excited $\mathrm{C}=\mathrm{C}$ stretching vibration that agrees well with the Raman scattering (RS) spectrum. In contrast, the EA spectrum of trans-${\left(\mathrm{CH}\right)}_{\mathrm{x}}$ does not match the first derivative of the material's absorption spectrum, and the phonon sideband frequency does not agree with the RS spectrum. In addition, the EA spectrum of trans-${\left(\mathrm{CH}\right)}_{\mathrm{x}}$ reveals a band below the first allowed $1B_{\mathrm{u}}$ exciton. We interpret this feature as due to the electric field activated even-parity dark (forbidden) exciton, namely $m{A}_{\mathrm{g}}$ ($m>2$), showing that the “nonluminescent” trans-${\left(\mathrm{CH}\right)}_{\mathrm{x}}$ is due to the reverse order of the excited states, where a series of dark $m{A}_{\mathrm{g}}$ excitons lies below the allowed $1B_{\mathrm{u}}$ exciton. This agrees with the unusual phonon sideband in trans-${\left(\mathrm{CH}\right)}_{\mathrm{x}}$ absorption, since the excited state attenuation caused by the fast internal conversion from $1B_{\mathrm{u}}$ to $m{A}_{\mathrm{g}}$ influences the apparent frequency that determines the phonon sideband. Consequently, from the EA and RS spectra we estimate the $1B_{\mathrm{u}}$ lifetime in trans-${\left(\mathrm{CH}\right)}_{\mathrm{x}}$ to be ∼30 fs. Moreover, the integrated EA spectrum of trans-${\left(\mathrm{CH}\right)}_{\mathrm{x}}$ shows a traditional Huang-Rhys type series with a relaxation parameter, $S$ ∼ 0.5. This indicates that the EA spectrum of the trans isomer is also determined by a Stark shift related to the first derivative of the absorption spectrum, but preferentially for the longest chains in the film's chain lengths distribution. This is due to the $N^3$ response of the nonlinear susceptibility, ${\chi }^{\left(3\right)}$ (∼EA), dependence on the chain length having $N$ monomers.

We consider the well-known phonon-scattering-induced high-temperature linear-in-$T$ metallic resistivity, showing that a naive extrapolation of the effective linearity from high temperatures to $T=0$ leads to an apparent zero-temperature negative resistivity. The precise magnitude of this extrapolated $T=0$ negative resistivity depends on the temperature regime from where the extrapolation is carried out, and approaches the correct physical result of zero resistivity at $T=0$ only if the extrapolation starts from $T\gg T_D$, where $T_D$ is the Debye temperature. We establish a theoretical relationship between the negative intercept and the slope of the linear-in-$T$ resistivity as a function of the temperature $T$ from where the extrapolation is carried out. Experimental implications of our finding are discussed for the much-discussed Planckian behavior of the transport scattering rate.