@article{19817, abstract = {We report a combined experimental and theoretical study of the surface and bulk electronic structure of aluminium diboride, a nonsuperconducting sister compound of the superconductor MgB2. We perform angle-resolved photoemission measurements with variable photon energy, and compare them to density functional theory calculations to disentangle the surface and bulk contributions to the measured spectra. Aluminium diboride is known to be aluminium deficient, Al1−𝛿⁢B2, which would be expected to lead to a hole doping as compared to the nominally stoichimoetric compound. Nonetheless, we find that the bulk 𝜎 states, which mediate superconductivity in MgB2, remain more than 600meV below the Fermi level. However, we also observe 𝜎 states originating from the boron terminated surface, with an order of magnitude smaller binding energy of 70meV, and demonstrate how surface hole-doping can bring these across the Fermi level.}, author = {Sunko, Veronika and Milosavljević, D. and Mazzola, F. and Clark, O. J. and Burkhardt, U. and Kim, T. K. and Rosner, H. and Grin, Yu. and Mackenzie, A. P. and King, P. D. C.}, issn = {2469-9969}, journal = {Physical Review B}, number = {3}, publisher = {American Physical Society}, title = {{Surface and bulk electronic structure of aluminium diboride}}, doi = {10.1103/physrevb.102.035143}, volume = {102}, year = {2020}, } @article{7933, abstract = {We study a mobile quantum impurity, possessing internal rotational degrees of freedom, confined to a ring in the presence of a many-particle bosonic bath. By considering the recently introduced rotating polaron problem, we define the Hamiltonian and examine the energy spectrum. The weak-coupling regime is studied by means of a variational ansatz in the truncated Fock space. The corresponding spectrum indicates that there emerges a coupling between the internal and orbital angular momenta of the impurity as a consequence of the phonon exchange. We interpret the coupling as a phonon-mediated spin-orbit coupling and quantify it by using a correlation function between the internal and the orbital angular momentum operators. The strong-coupling regime is investigated within the Pekar approach, and it is shown that the correlation function of the ground state shows a kink at a critical coupling, that is explained by a sharp transition from the noninteracting state to the states that exhibit strong interaction with the surroundings. The results might find applications in such fields as spintronics or topological insulators where spin-orbit coupling is of crucial importance.}, author = {Maslov, Mikhail and Lemeshko, Mikhail and Yakaboylu, Enderalp}, issn = {2469-9969}, journal = {Physical Review B}, number = {18}, publisher = {American Physical Society}, title = {{Synthetic spin-orbit coupling mediated by a bosonic environment}}, doi = {10.1103/PhysRevB.101.184104}, volume = {101}, year = {2020}, } @article{7971, abstract = {Multilayer graphene lattices allow for an additional tunability of the band structure by the strong perpendicular electric field. In particular, the emergence of the new multiple Dirac points in ABA stacked trilayer graphene subject to strong transverse electric fields was proposed theoretically and confirmed experimentally. These new Dirac points dubbed “gullies” emerge from the interplay between strong electric field and trigonal warping. In this work, we first characterize the properties of new emergent Dirac points and show that the electric field can be used to tune the distance between gullies in the momentum space. We demonstrate that the band structure has multiple Lifshitz transitions and higher-order singularity of “monkey saddle” type. Following the characterization of the band structure, we consider the spectrum of Landau levels and structure of their wave functions. In the limit of strong electric fields when gullies are well separated in momentum space, they give rise to triply degenerate Landau levels. In the second part of this work, we investigate how degeneracy between three gully Landau levels is lifted in the presence of interactions. Within the Hartree-Fock approximation we show that the symmetry breaking state interpolates between the fully gully polarized state that breaks C3 symmetry at high displacement field and the gully symmetric state when the electric field is decreased. The discontinuous transition between these two states is driven by enhanced intergully tunneling and exchange. We conclude by outlining specific experimental predictions for the existence of such a symmetry-breaking state.}, author = {Rao, Peng and Serbyn, Maksym}, issn = {2469-9969}, journal = {Physical Review B}, number = {24}, publisher = {American Physical Society}, title = {{Gully quantum Hall ferromagnetism in biased trilayer graphene}}, doi = {10.1103/physrevb.101.245411}, volume = {101}, year = {2020}, } @article{8308, abstract = {Many-body localization provides a mechanism to avoid thermalization in isolated interacting quantum systems. The breakdown of thermalization may be complete, when all eigenstates in the many-body spectrum become localized, or partial, when the so-called many-body mobility edge separates localized and delocalized parts of the spectrum. Previously, De Roeck et al. [Phys. Rev. B 93, 014203 (2016)] suggested a possible instability of the many-body mobility edge in energy density. The local ergodic regions—so-called “bubbles”—resonantly spread throughout the system, leading to delocalization. In order to study such instability mechanism, in this work we design a model featuring many-body mobility edge in particle density: the states at small particle density are localized, while increasing the density of particles leads to delocalization. Using numerical simulations with matrix product states, we demonstrate the stability of many-body localization with respect to small bubbles in large dilute systems for experimentally relevant timescales. In addition, we demonstrate that processes where the bubble spreads are favored over processes that lead to resonant tunneling, suggesting a possible mechanism behind the observed stability of many-body mobility edge. We conclude by proposing experiments to probe particle density mobility edge in the Bose-Hubbard model.}, author = {Brighi, Pietro and Abanin, Dmitry A. and Serbyn, Maksym}, issn = {2469-9969}, journal = {Physical Review B}, number = {6}, publisher = {American Physical Society}, title = {{Stability of mobility edges in disordered interacting systems}}, doi = {10.1103/physrevb.102.060202}, volume = {102}, year = {2020}, } @article{8588, abstract = {Dipolar (or spatially indirect) excitons (IXs) in semiconductor double quantum well (DQW) subjected to an electric field are neutral species with a dipole moment oriented perpendicular to the DQW plane. Here, we theoretically study interactions between IXs in stacked DQW bilayers, where the dipolar coupling can be either attractive or repulsive depending on the relative positions of the particles. By using microscopic band structure calculations to determine the electronic states forming the excitons, we show that the attractive dipolar interaction between stacked IXs deforms their electronic wave function, thereby increasing the inter-DQW interaction energy and making the IX even more electrically polarizable. Many-particle interaction effects are addressed by considering the coupling between a single IX in one of the DQWs to a cloud of IXs in the other DQW, which is modeled either as a closed-packed lattice or as a continuum IX fluid. We find that the lattice model yields IX interlayer binding energies decreasing with increasing lattice density. This behavior is due to the dominating role of the intra-DQW dipolar repulsion, which prevents more than one exciton from entering the attractive region of the inter-DQW coupling. Finally, both models shows that the single IX distorts the distribution of IXs in the adjacent DQW, thus inducing the formation of an IX dipolar polaron (dipolaron). While the interlayer binding energy reduces with IX density for lattice dipolarons, the continuous polaron model predicts a nonmonotonous dependence on density in semiquantitative agreement with a recent experimental study [cf. Hubert et al., Phys. Rev. X 9, 021026 (2019)].}, author = {Hubert, C. and Cohen, K. and Ghazaryan, Areg and Lemeshko, Mikhail and Rapaport, R. and Santos, P. V.}, issn = {2469-9969}, journal = {Physical Review B}, number = {4}, publisher = {American Physical Society}, title = {{Attractive interactions, molecular complexes, and polarons in coupled dipolar exciton fluids}}, doi = {10.1103/physrevb.102.045307}, volume = {102}, year = {2020}, } @article{8769, abstract = {One of the hallmarks of quantum statistics, tightly entwined with the concept of topological phases of matter, is the prediction of anyons. Although anyons are predicted to be realized in certain fractional quantum Hall systems, they have not yet been unambiguously detected in experiment. Here we introduce a simple quantum impurity model, where bosonic or fermionic impurities turn into anyons as a consequence of their interaction with the surrounding many-particle bath. A cloud of phonons dresses each impurity in such a way that it effectively attaches fluxes or vortices to it and thereby converts it into an Abelian anyon. The corresponding quantum impurity model, first, provides a different approach to the numerical solution of the many-anyon problem, along with a concrete perspective of anyons as emergent quasiparticles built from composite bosons or fermions. More importantly, the model paves the way toward realizing anyons using impurities in crystal lattices as well as ultracold gases. In particular, we consider two heavy electrons interacting with a two-dimensional lattice crystal in a magnetic field, and show that when the impurity-bath system is rotated at the cyclotron frequency, impurities behave as anyons as a consequence of the angular momentum exchange between the impurities and the bath. A possible experimental realization is proposed by identifying the statistics parameter in terms of the mean-square distance of the impurities and the magnetization of the impurity-bath system, both of which are accessible to experiment. Another proposed application is impurities immersed in a two-dimensional weakly interacting Bose gas.}, author = {Yakaboylu, Enderalp and Ghazaryan, Areg and Lundholm, D. and Rougerie, N. and Lemeshko, Mikhail and Seiringer, Robert}, issn = {2469-9969}, journal = {Physical Review B}, number = {14}, publisher = {American Physical Society}, title = {{Quantum impurity model for anyons}}, doi = {10.1103/physrevb.102.144109}, volume = {102}, year = {2020}, } @article{8944, abstract = {Superconductor insulator transition in transverse magnetic field is studied in the highly disordered MoC film with the product of the Fermi momentum and the mean free path kF*l close to unity. Surprisingly, the Zeeman paramagnetic effects dominate over orbital coupling on both sides of the transition. In superconducting state it is evidenced by a high upper critical magnetic field 𝐵𝑐2, by its square root dependence on temperature, as well as by the Zeeman splitting of the quasiparticle density of states (DOS) measured by scanning tunneling microscopy. At 𝐵𝑐2 a logarithmic anomaly in DOS is observed. This anomaly is further enhanced in increasing magnetic field, which is explained by the Zeeman splitting of the Altshuler-Aronov DOS driving the system into a more insulating or resistive state. Spin dependent Altshuler-Aronov correction is also needed to explain the transport behavior above 𝐵𝑐2.}, author = {Zemlicka, Martin and Kopčík, M. and Szabó, P. and Samuely, T. and Kačmarčík, J. and Neilinger, P. and Grajcar, M. and Samuely, P.}, issn = {2469-9969}, journal = {Physical Review B}, number = {18}, publisher = {American Physical Society}, title = {{Zeeman-driven superconductor-insulator transition in strongly disordered MoC films: Scanning tunneling microscopy and transport studies in a transverse magnetic field}}, doi = {10.1103/PhysRevB.102.180508}, volume = {102}, year = {2020}, } @article{7428, abstract = {In the superconducting regime of FeTe(1−x)Sex, there exist two types of vortices which are distinguished by the presence or absence of zero-energy states in their core. To understand their origin, we examine the interplay of Zeeman coupling and superconducting pairings in three-dimensional metals with band inversion. Weak Zeeman fields are found to suppress intraorbital spin-singlet pairing, known to localize the states at the ends of the vortices on the surface. On the other hand, an orbital-triplet pairing is shown to be stable against Zeeman interactions, but leads to delocalized zero-energy Majorana modes which extend through the vortex. In contrast, the finite-energy vortex modes remain localized at the vortex ends even when the pairing is of orbital-triplet form. Phenomenologically, this manifests as an observed disappearance of zero-bias peaks within the cores of topological vortices upon an increase of the applied magnetic field. The presence of magnetic impurities in FeTe(1−x)Sex, which are attracted to the vortices, would lead to such Zeeman-induced delocalization of Majorana modes in a fraction of vortices that capture a large enough number of magnetic impurities. Our results provide an explanation for the dichotomy between topological and nontopological vortices recently observed in FeTe(1−x)Sex.}, author = {Ghazaryan, Areg and Lopes, P. L.S. and Hosur, Pavan and Gilbert, Matthew J. and Ghaemi, Pouyan}, issn = {2469-9969}, journal = {Physical Review B}, number = {2}, publisher = {American Physical Society}, title = {{Effect of Zeeman coupling on the Majorana vortex modes in iron-based topological superconductors}}, doi = {10.1103/PhysRevB.101.020504}, volume = {101}, year = {2020}, } @article{6174, abstract = {We propose a scaling theory for the many-body localization (MBL) phase transition in one dimension, building on the idea that it proceeds via a “quantum avalanche.” We argue that the critical properties can be captured at a coarse-grained level by a Kosterlitz-Thouless (KT) renormalization group (RG) flow. On phenomenological grounds, we identify the scaling variables as the density of thermal regions and the length scale that controls the decay of typical matrix elements. Within this KT picture, the MBL phase is a line of fixed points that terminates at the delocalization transition. We discuss two possible scenarios distinguished by the distribution of rare, fractal thermal inclusions within the MBL phase. In the first scenario, these regions have a stretched exponential distribution in the MBL phase. In the second scenario, the near-critical MBL phase hosts rare thermal regions that are power-law-distributed in size. This points to the existence of a second transition within the MBL phase, at which these power laws change to the stretched exponential form expected at strong disorder. We numerically simulate two different phenomenological RGs previously proposed to describe the MBL transition. Both RGs display a universal power-law length distribution of thermal regions at the transition with a critical exponent αc=2, and continuously varying exponents in the MBL phase consistent with the KT picture.}, author = {Dumitrescu, Philipp T. and Goremykina, Anna and Parameswaran, Siddharth A. and Serbyn, Maksym and Vasseur, Romain}, issn = {2469-9969}, journal = {Physical Review B}, number = {9}, publisher = {American Physical Society}, title = {{Kosterlitz-Thouless scaling at many-body localization phase transitions}}, doi = {10.1103/physrevb.99.094205}, volume = {99}, year = {2019}, } @article{19826, abstract = {We investigate the electronic structure of a two-dimensional electron gas created at the surface of the multivalley semimetal 1⁢T −PtSe2. Using angle-resolved photoemission and first-principles-based surface space-charge calculations, we show how the induced quantum well sub-band states form multiple Fermi surfaces, which exhibit highly anisotropic Rashba-like spin splittings. We further show how the presence of both electronlike and holelike bulk carriers causes the near-surface band bending potential to develop an unusual nonmonotonic form, with spatially segregated electron accumulation and hole accumulation regions, which in turn amplifies the induced spin splitting. Our results thus demonstrate the novel environment that semimetals provide for tailoring electrostatically induced potential profiles and their corresponding quantum sub-band states.}, author = {Clark, O. J. and Mazzola, F. and Feng, J. and Sunko, Veronika and Marković, I. and Bawden, L. and Kim, T. K. and King, P. D. C. and Bahramy, M. S.}, issn = {2469-9969}, journal = {Physical Review B}, number = {4}, publisher = {American Physical Society}, title = {{Dual quantum confinement and anisotropic spin splitting in the multivalley semimetal PtSe2}}, doi = {10.1103/physrevb.99.045438}, volume = {99}, year = {2019}, } @article{7013, abstract = {Chains of superconducting circuit devices provide a natural platform for studies of synthetic bosonic quantum matter. Motivated by the recent experimental progress in realizing disordered and interacting chains of superconducting transmon devices, we study the bosonic many-body localization phase transition using the methods of exact diagonalization as well as matrix product state dynamics. We estimate the location of transition separating the ergodic and the many-body localized phases as a function of the disorder strength and the many-body on-site interaction strength. The main difference between the bosonic model realized by superconducting circuits and similar fermionic model is that the effect of the on-site interaction is stronger due to the possibility of multiple excitations occupying the same site. The phase transition is found to be robust upon including longer-range hopping and interaction terms present in the experiments. Furthermore, we calculate experimentally relevant local observables and show that their temporal fluctuations can be used to distinguish between the dynamics of Anderson insulator, many-body localization, and delocalized phases. While we consider unitary dynamics, neglecting the effects of dissipation, decoherence, and measurement back action, the timescales on which the dynamics is unitary are sufficient for observation of characteristic dynamics in the many-body localized phase. Moreover, the experimentally available disorder strength and interactions allow for tuning the many-body localization phase transition, thus making the arrays of superconducting circuit devices a promising platform for exploring localization physics and phase transition.}, author = {Orell, Tuure and Michailidis, Alexios and Serbyn, Maksym and Silveri, Matti}, issn = {2469-9969}, journal = {Physical Review B}, number = {13}, publisher = {American Physical Society}, title = {{Probing the many-body localization phase transition with superconducting circuits}}, doi = {10.1103/physrevb.100.134504}, volume = {100}, year = {2019}, } @article{7015, abstract = {We modify the "floating crystal" trial state for the classical homogeneous electron gas (also known as jellium), in order to suppress the boundary charge fluctuations that are known to lead to a macroscopic increase of the energy. The argument is to melt a thin layer of the crystal close to the boundary and consequently replace it by an incompressible fluid. With the aid of this trial state we show that three different definitions of the ground-state energy of jellium coincide. In the first point of view the electrons are placed in a neutralizing uniform background. In the second definition there is no background but the electrons are submitted to the constraint that their density is constant, as is appropriate in density functional theory. Finally, in the third system each electron interacts with a periodic image of itself; that is, periodic boundary conditions are imposed on the interaction potential.}, author = {Lewin, Mathieu and Lieb, Elliott H. and Seiringer, Robert}, issn = {2469-9969}, journal = {Physical Review B}, number = {3}, publisher = {American Physical Society}, title = {{Floating Wigner crystal with no boundary charge fluctuations}}, doi = {10.1103/physrevb.100.035127}, volume = {100}, year = {2019}, } @article{7145, abstract = {End-to-end correlated bound states are investigated in superconductor-semiconductor hybrid nanowires at zero magnetic field. Peaks in subgap conductance are independently identified from each wire end, and a cross-correlation function is computed that counts end-to-end coincidences, averaging over thousands of subgap features. Strong correlations in a short, 300-nm device are reduced by a factor of 4 in a long, 900-nm device. In addition, subgap conductance distributions are investigated, and correlations between the left and right distributions are identified based on their mutual information.}, author = {Anselmetti, G. L. R. and Martinez, E. A. and Ménard, G. C. and Puglia, D. and Malinowski, F. K. and Lee, J. S. and Choi, S. and Pendharkar, M. and Palmstrøm, C. J. and Marcus, C. M. and Casparis, L. and Higginbotham, Andrew P}, issn = {2469-9969}, journal = {Physical Review B}, number = {20}, publisher = {American Physical Society}, title = {{End-to-end correlated subgap states in hybrid nanowires}}, doi = {10.1103/physrevb.100.205412}, volume = {100}, year = {2019}, } @article{7200, abstract = {Recent scanning tunneling microscopy experiments in NbN thin disordered superconducting films found an emergent inhomogeneity at the scale of tens of nanometers. This inhomogeneity is mirrored by an apparent dimensional crossover in the paraconductivity measured in transport above the superconducting critical temperature Tc. This behavior was interpreted in terms of an anomalous diffusion of fluctuating Cooper pairs that display a quasiconfinement (i.e., a slowing down of their diffusive dynamics) on length scales shorter than the inhomogeneity identified by tunneling experiments. Here, we assume this anomalous diffusive behavior of fluctuating Cooper pairs and calculate the effect of these fluctuations on the electron density of states above Tc. We find that the density of states is substantially suppressed up to temperatures well above Tc. This behavior, which is closely reminiscent of a pseudogap, only arises from the anomalous diffusion of fluctuating Cooper pairs in the absence of stable preformed pairs, setting the stage for an intermediate behavior between the two common paradigms in the superconducting-insulator transition, namely, the localization of Cooper pairs (the so-called bosonic scenario) and the breaking of Cooper pairs into unpaired electrons due to strong disorder (the so-called fermionic scenario).}, author = {Brighi, Pietro and Grilli, Marco and Leridon, Brigitte and Caprara, Sergio}, issn = {2469-9969}, journal = {Physical Review B}, number = {17}, publisher = {American Physical Society}, title = {{Effect of anomalous diffusion of fluctuating Cooper pairs on the density of states of superconducting NbN thin films}}, doi = {10.1103/PhysRevB.100.174518}, volume = {100}, year = {2019}, } @article{5983, abstract = {We study a quantum impurity possessing both translational and internal rotational degrees of freedom interacting with a bosonic bath. Such a system corresponds to a “rotating polaron,” which can be used to model, e.g., a rotating molecule immersed in an ultracold Bose gas or superfluid helium. We derive the Hamiltonian of the rotating polaron and study its spectrum in the weak- and strong-coupling regimes using a combination of variational, diagrammatic, and mean-field approaches. We reveal how the coupling between linear and angular momenta affects stable quasiparticle states, and demonstrate that internal rotation leads to an enhanced self-localization in the translational degrees of freedom.}, author = {Yakaboylu, Enderalp and Midya, Bikashkali and Deuchert, Andreas and Leopold, Nikolai K and Lemeshko, Mikhail}, issn = {2469-9969}, journal = {Physical Review B}, number = {22}, publisher = {American Physical Society}, title = {{Theory of the rotating polaron: Spectrum and self-localization}}, doi = {10.1103/physrevb.98.224506}, volume = {98}, year = {2018}, } @article{6369, abstract = {We construct a metamaterial from radio-frequency harmonic oscillators, and find two topologically distinct phases resulting from dissipation engineered into the system. These phases are distinguished by a quantized value of bulk energy transport. The impulse response of our circuit is measured and used to reconstruct the band structure and winding number of circuit eigenfunctions around a dark mode. Our results demonstrate that dissipative topological transport can occur in a wider class of physical systems than considered before.}, author = {Rosenthal, Eric I. and Ehrlich, Nicole K. and Rudner, Mark S. and Higginbotham, Andrew P and Lehnert, K. W.}, issn = {2469-9950}, journal = {Physical Review B}, number = {22}, publisher = {American Physical Society (APS)}, title = {{Topological phase transition measured in a dissipative metamaterial}}, doi = {10.1103/physrevb.97.220301}, volume = {97}, year = {2018}, } @article{10627, abstract = {We present a scanning probe technique for measuring the dynamics of individual fluxoid transitions in multiply connected superconducting structures. In these measurements, a small magnetic particle attached to the tip of a silicon cantilever is scanned over a micron-size superconducting ring fabricated from a thin aluminum film. We find that near the superconducting transition temperature of the aluminum, the dissipation and frequency of the cantilever changes significantly at particular locations where the tip-induced magnetic flux penetrating the ring causes the two lowest-energy fluxoid states to become nearly degenerate. In this regime, we show that changes in the cantilever frequency and dissipation are well-described by a stochastic resonance (SR) process, wherein small oscillations of the cantilever in the presence of thermally activated phase slips (TAPS) in the ring give rise to a dynamical force that modifies the mechanical properties of the cantilever. Using the SR model, we calculate the average fluctuation rate of the TAPS as a function of temperature over a 32-dB range in frequency, and we compare it to the Langer-Ambegaokar-McCumber-Halperin theory for TAPS in one-dimensional superconducting structures.}, author = {Polshyn, Hryhoriy and Naibert, Tyler R. and Budakian, Raffi}, issn = {2469-9969}, journal = {Physical Review B}, number = {18}, publisher = {American Physical Society}, title = {{Imaging phase slip dynamics in micron-size superconducting rings}}, doi = {10.1103/physrevb.97.184501}, volume = {97}, year = {2018}, } @article{9687, abstract = {The Gibbs free energy is the fundamental thermodynamic potential underlying the relative stability of different states of matter under constant-pressure conditions. However, computing this quantity from atomic-scale simulations is far from trivial, so the potential energy of a system is often used as a proxy. In this paper, we use a combination of thermodynamic integration methods to accurately evaluate the Gibbs free energies associated with defects in crystals, including the vacancy formation energy in bcc iron, and the stacking fault energy in fcc nickel, iron, and cobalt. We quantify the importance of entropic and anharmonic effects in determining the free energies of defects at high temperatures, and show that the potential energy approximation as well as the harmonic approximation may produce inaccurate or even qualitatively wrong results. Our calculations manifest the necessity to employ accurate free energy methods such as thermodynamic integration to estimate the stability of crystallographic defects at high temperatures.}, author = {Cheng, Bingqing and Ceriotti, Michele}, issn = {2469-9969}, journal = {Physical Review B}, number = {5}, publisher = {American Physical Society}, title = {{Computing the absolute Gibbs free energy in atomistic simulations: Applications to defects in solids}}, doi = {10.1103/physrevb.97.054102}, volume = {97}, year = {2018}, } @article{7058, abstract = {We examine recent magnetic torque measurements in two compounds, γ−Li2IrO3 and RuCl3, which have been discussed as possible realizations of the Kitaev model. The analysis of the reported discontinuity in torque, as an external magnetic field is rotated across the c axis in both crystals, suggests that they have a translationally invariant chiral spin order of the form ⟨Si⋅(Sj×Sk)⟩≠0 in the ground state and persisting over a very wide range of magnetic field and temperature. An extraordinary |B|B2 dependence of the torque for small fields, beside the usual B2 part, is predicted by the chiral spin order. Data for small fields are available for γ−Li2IrO3 and are found to be consistent with the prediction upon further analysis. Other experiments such as inelastic scattering and thermal Hall effect and several questions raised by the discovery of chiral spin order, including its topological consequences, are discussed.}, author = {Modic, Kimberly A and Ramshaw, B. J. and Shekhter, A. and Varma, C. M.}, issn = {2469-9969}, journal = {Physical Review B}, number = {20}, publisher = {APS}, title = {{Chiral spin order in some purported Kitaev spin-liquid compounds}}, doi = {10.1103/physrevb.98.205110}, volume = {98}, year = {2018}, } @article{1162, abstract = {Selected universal experimental properties of high-temperature superconducting (HTS) cuprates have been singled out in the last decade. One of the pivotal challenges in this field is the designation of a consistent interpretation framework within which we can describe quantitatively the universal features of those systems. Here we analyze in a detailed manner the principal experimental data and compare them quantitatively with the approach based on a single-band model of strongly correlated electrons supplemented with strong antiferromagnetic (super)exchange interaction (the so-called t−J−U model). The model rationale is provided by estimating its microscopic parameters on the basis of the three-band approach for the Cu-O plane. We use our original full Gutzwiller wave-function solution by going beyond the renormalized mean-field theory (RMFT) in a systematic manner. Our approach reproduces very well the observed hole doping (δ) dependence of the kinetic-energy gain in the superconducting phase, one of the principal non-Bardeen-Cooper-Schrieffer features of the cuprates. The calculated Fermi velocity in the nodal direction is practically δ-independent and its universal value agrees very well with that determined experimentally. Also, a weak doping dependence of the Fermi wave vector leads to an almost constant value of the effective mass in a pure superconducting phase which is both observed in experiment and reproduced within our approach. An assessment of the currently used models (t−J, Hubbard) is carried out and the results of the canonical RMFT as a zeroth-order solution are provided for comparison to illustrate the necessity of the introduced higher-order contributions.}, author = {Spałek, Jozef and Zegrodnik, Michał and Kaczmarczyk, Jan}, issn = {2469-9950}, journal = {Physical Review B - Condensed Matter and Materials Physics}, number = {2}, publisher = {American Physical Society}, title = {{Universal properties of high temperature superconductors from real space pairing t-J-U model and its quantitative comparison with experiment}}, doi = {10.1103/PhysRevB.95.024506}, volume = {95}, year = {2017}, }