A5075311043- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Cold Atom Physics and Bose-Einstein Condensates
- Quantum and electron transport phenomena
- Magnetic and transport properties of perovskites and related materials
- Quantum many-body systems
- Quantum, superfluid, helium dynamics
- Topological Materials and Phenomena
- Theoretical and Computational Physics
- Graphene research and applications
- 2D Materials and Applications
- Atomic and Subatomic Physics Research
- Electronic and Structural Properties of Oxides
- Iron-based superconductors research
- Rare-earth and actinide compounds
- Surface and Thin Film Phenomena
- Magnetic properties of thin films
- Multiferroics and related materials
- Organic and Molecular Conductors Research
- Perovskite Materials and Applications
- Advanced Thermodynamics and Statistical Mechanics
- Chalcogenide Semiconductor Thin Films
- High-pressure geophysics and materials
- Thermal Expansion and Ionic Conductivity
- Quantum Information and Cryptography
The Ohio State University
2016-2025
Charotar University of Science and Technology
2023-2024
Wrocław University of Science and Technology
2020
AGH University of Krakow
2020
University of Stuttgart
2012
Cornell University
1987-2010
Tata Institute of Fundamental Research
1996-2005
University of Illinois Urbana-Champaign
1988-2005
University of Pennsylvania
1998
Argonne National Laboratory
1991-1997
Strong electron correlations lie at the origin of high-temperature superconductivity. Its essence is believed to be captured by Fermi-Hubbard model repulsively interacting fermions on a lattice. Here we report site-resolved observation charge and spin in two-dimensional (2D) realized with ultracold atoms. Antiferromagnetic are maximal half-filling weaken monotonically upon doping. At large doping, nearest-neighbor between singly charged sites negative, revealing formation correlation hole,...
We use ultrahigh resolution, tunable, vacuum ultraviolet laser-based, angle-resolved photoemission spectroscopy (ARPES), temperature- and field-dependent resistivity, thermoelectric power (TEP) measurements to study the electronic properties of ${\mathrm{WTe}}_{2}$, a compound that manifests exceptionally large, temperature-dependent magnetoresistance. The Fermi surface consists two pairs electron hole pockets along $X\text{\ensuremath{-}}\mathrm{\ensuremath{\Gamma}}\text{\ensuremath{-}}X$...
We lay the foundation for determining microscopic spin interactions in two-dimensional (2D) ferromagnets by combining angle-dependent ferromagnetic resonance (FMR) experiments on high quality CrI$_3$ single crystals with theoretical modeling based symmetries. discover that Kitaev interaction is strongest this material $K \sim -5.2$ meV, 25 times larger than Heisenberg exchange $J -0.2$ and responsible opening $\sim$5 meV gap at Dirac points spin-wave dispersion. Furthermore, we find...
We study the normal state of 2D attractive Hubbard model using quantum Monte Carlo simulations. show that singlet pairing correlations develop above ${\mathit{T}}_{\mathit{c}}$, and a short coherence length superconductor deviates from canonical Fermi liquid. In intermediate U regime, spin susceptibility ${\mathrm{\ensuremath{\chi}}}_{\mathit{s}}$ is strongly temperature dependent, low-frequency spectral weight, as measured by NMR relaxation rate 1/${\mathit{T}}_{1}$T, shown to track...
One of the first theoretical proposals for understanding high temperature superconductivity in cuprates was Anderson's RVB theory using a Gutzwiller projected BCS wave function as an approximate ground state. Recent work by Paramekanti, Randeria and Trivedi has shown that this variational approach gives semi-quantitative doping dependences variety experimental observables superconducting state cuprates. In paper we revisit these issues ``renormalized mean field theory'' Zhang, Gros, Rice...
We study a simple model of two-dimensional s-wave superconductor in the presence random potential regime large disorder. first use Bogoliubov-de Gennes (BdG) approach to show that, with increasing disorder pairing amplitude becomes spatially inhomogeneous, and system cannot be described within conventional approaches for studying disordered superconductors which assume uniform order parameter. In high regime, we find that breaks up into superconducting islands (with amplitude) separated by...
We present results of path-integral Monte Carlo simulations bosons on a two-dimensional square lattice in random potential average strength V and with on-site repulsion U. find that the superfluid density ${\mathrm{\ensuremath{\rho}}}_{\mathit{s}}$ is enhanced by increasing U certain regions parameter space. By combining ${\mathrm{\ensuremath{\rho}}}_{\mathit{s}}$, behavior density-density correlation function lattices size up to 10\ifmmode\times\else\texttimes\fi{}10, we study...
The effect of nonmagnetic impurities on 2D $s$-wave superconductors is studied beyond the weak disorder regime. Within Bogoliubov--de Gennes (BdG) framework, local pairing amplitude develops a broad distribution with significant weight near zero increasing disorder. Surprisingly, density states continues to show finite spectral gap. persistence gap at large shown arise from breakup system into superconducting ``islands.'' Superfluid and off-diagonal correlations substantial reduction high A...
The confinement of electrons in small dimensions can lead to a discretization energy levels. associated quantum size effects turn an out-of-plane conductivity that shows nonanalytic behavior the approach classical limit. principal dependence is \ensuremath{\sim}1/d for film thickness d; however, there also correction term has essential singularity parameter l/d, where l mean free path bulk sample. Surface roughness introduced by establishing two physical length scales. Variations d on scales...
We study the Hubbard model with parameters relevant to cuprates using variational Monte Carlo for projected d-wave states. For doping 0<x approximately less than or equal 0.35 we obtain a superconductor whose order parameter Phi(x) tracks observed nonmonotonic T(c)(x). The Delta(var)(x) scales (pi,0) "hump" and T* seen in photoemission. Projection leads incoherence spectral function from singular behavior of its moments nodal quasiparticle weight Z x though Fermi velocity remains finite as...
We have studied via a Green-function Monte Carlo (GFMC) method the S=(1/2 Heisenberg quantum antiferromagnet in two dimensions. use well-known transformation to map spin problem onto system of hard-core bosons that allows us exploit interesting analogies between magnetism and superfluidity. The GFMC is zero-temperature stochastic projects out component true ground state given variational wave function. This complementary previously used finite-temperature methods well suited studying...
We show that there are qualitative differences between the temperature dependence of spin and charge correlations in normal state 2D attractive Hubbard model using quantum Monte Carlo simulations. The one-particle density states shows a pseudogap above $\tc$ with depleted $N(0)$ decreasing $T$. susceptibility $\cs$ low frequency spectral weight track $N(0)$, which explains spin-gap scaling: $1/T_1T \sim \cs(T)$. However channel is dominated by collective behavior compressibility $dn/d\mu$...
Motivated by the experimental realization of synthetic spin-orbit coupling for ultracold atoms, we investigate phase diagram Bose Hubbard model in a non-abelian gauge field two dimensions. Using strong expansion combined presence and tunable interactions, find variety interesting magnetic Hamiltonians Mott insulator (MI), which support textures such as spin spirals vortex Skyrmion crystals. An inhomogeneous mean treatment shows that superfluid (SF) phases inherit these exotic orders from MI...
We use a variational approach to gain insight into the strongly correlated $d$-wave superconducting state of high ${T}_{c}$ cuprates at $T=0$. show that strong correlations lead qualitatively different trends in pairing and phase coherence: scale decreases monotonically with hole doping while order parameter shows nonmonotonic dome. obtain detailed results for dependence large number experimentally observable quantities, including chemical potential, coherence length, momentum distribution,...
Understanding the magnetic response of normal state cuprates is considered a key piece in solving puzzle their high-temperature superconductivity. The essential physics these materials believed to be captured by Fermi-Hubbard model, minimal model that has been realized with cold atoms optical lattices. Here we report on site-resolved measurements spin-imbalanced atomic gas, allowing us explore system large effective fields. We observe short-range canted antiferromagnetism at half-filling...
A charge-density wave (CDW) state has a broken symmetry described by complex order parameter with an amplitude and phase. The conventional view, based on clean, weak-coupling systems, is that finite long-range phase coherence set in simultaneously at the CDW transition temperature T$_{cdw}$. Here we investigate, using photoemission, X-ray scattering scanning tunneling microscopy, canonical compound 2H-NbSe$_2$ intercalated Mn Co, show view untenable. We find that, either high or large...
One of the major challenges in realizing antiferromagnetic and superfluid phases optical lattices is ability to cool fermions. We determine constraints on entropy for observing these two-dimensional Hubbard models using determinantal quantum Monte Carlo simulations. find that an per particle approximately = ln2 sufficient observe insulating gap repulsive model at half-filling, or pairing pseudogap attractive case. Observing correlations superfluidity 2D systems requires a further reduction...
Weyl semimetals expand research on topologically protected transport by adding bulk Berry monopoles with linearly dispersing electronic states and robust, gapless surface Fermi arcs terminating node projections. Here, we show how the Nernst effect, combining entropy charge transport, gives a unique signature for presence of Dirac bands. The thermopower NbP (maximum 800 microV K-1 at 9 T, 109 K) exceeds its conventional hundredfold is significantly larger than traditional thermoelectric...
We consider the electromagnetic response of a topological Weyl semimetal (TWS) with pair nodes in bulk and corresponding Fermi arcs surface Brillouin zone. compute frequency-dependent complex conductivities $\sigma_{\alpha\beta}(\omega)$ also take into account modification Maxwell equations by $\theta$-term to obtain Kerr Faraday rotations variety geometries. For TWS films thinner than wavelength, rotations, determined separation between nodes, are significantly larger insulators. In thicker...