A5085112919- Physics of Superconductivity and Magnetism
- Quantum and electron transport phenomena
- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Theoretical and Computational Physics
- Iron-based superconductors research
- Organic and Molecular Conductors Research
- Cold Atom Physics and Bose-Einstein Condensates
- Rare-earth and actinide compounds
- Quantum, superfluid, helium dynamics
- Quantum many-body systems
- Superconductivity in MgB2 and Alloys
- Advanced Chemical Physics Studies
- Surface and Thin Film Phenomena
- Magnetic properties of thin films
- Topological Materials and Phenomena
- Mechanical and Optical Resonators
- Superconducting Materials and Applications
- High-pressure geophysics and materials
- Electronic and Structural Properties of Oxides
- Graphene research and applications
- Quantum chaos and dynamical systems
- Molecular Junctions and Nanostructures
- Semiconductor Quantum Structures and Devices
- Fullerene Chemistry and Applications
Stanford University
2016-2025
SLAC National Accelerator Laboratory
2010-2024
University of Oxford
2023-2024
Princeton University
2020
University of Minnesota
2017
University of California, Santa Barbara
1985-2015
University of California, Los Angeles
1999-2013
University of California, Irvine
2011
California Institute of Technology
2010
Binghamton University
2010
Self-localized nonlinear excitations (solitons, polarons, and bipolarons) are fundamental inherent features of quasi-one-dimensional conducting polymers. Their signatures evident in many aspects the physical chemical properties this growing class novel materials. As a result, these polymers represent an opportunity for exploring phenomena associated with topological solitons their linear confinement which results from weakly lifting ground-state degeneracy. The authors review theoretical...
This article discusses fluctuating order in a quantum disordered phase proximate to critical point, with particular emphasis on stripe order. Optimal strategies are derived for extracting information concerning such local from experiments, neutron scattering and scanning tunneling microscopy. These ideas tested by application two model systems---an exactly solvable one-dimensional (1D) electron gas an impurity, weakly interacting 2D gas. Experiments the cuprate high-temperature...
We discuss the short-range resonating-valence-bond system as realized by a quantum hard-core dimer gas of arbitrary density on two-dimensional square lattice. When dimers completely cover lattice, we argue that there is first-order transition from crystal to an insulating liquid state which possesses low-energy, neutral, spinless excitations call "resonons." For less than close-packed densities, ground superfluid. In addition usual Goldstone mode, are zone-boundary excitations.
We study the two-dimensional electron gas in a high magnetic field at filling factor \ensuremath{\nu}=1 for an arbitrary ratio of Zeeman energy g${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$B to typical interaction energy. find that system always has gap, even when one-particle gap vanishes, i.e., g=0. When g is sufficiently large, quasiparticles are perturbatively related those noninteracting limit; we compute their energies second order Coulomb interaction. For smaller than critical value...
Starting directly from the microscopic Hamiltonian, we derive a field-theory model for fractional quantum Hall effect. By considering an approximate coarse-grained version of same model, construct Landau-Ginzburg theory similar to that Girvin. The partition function exhibits cusps as density and conductance is quantized at filling factors $\ensuremath{\nu}={(2k\ensuremath{-}1)}^{\ensuremath{-}1}$ with $k$ arbitrary integer. At these fractions ground state incompressible, quasiparticles...
The electronic phase diagrams of many highly correlated systems, and in particular the cuprate high temperature superconductors, are complex, with different phases appearing similar-sometimes identical-ordering temperatures even as material properties, such a dopant concentration, varied over wide ranges. This complexity is sometimes referred to "competing orders." However, since relation intimate, can lead existence new matter putative "pair-density-wave," general better thought terms...
It is shown that, for the t-J model, dilute holes in an antiferromagnet are unstable against phase separation into a hole-rich and no-hole phase. When spin-exchange interaction J exceeds critical value ${J}_{c}$, has no electrons. proposed that slightly less than ${J}_{c}$ low-density superfluid of electron pairs. A brief discussion other related models given.
We study the topological order in resonating valence-bond state. The elementary excitations have reversed charge-statistics relations: There are neutral spin-1/2 fermions and charge \ifmmode\pm\else\textpm\fi{}e spinless bosons, analogous to solitons polyacetylene. charged very light, form a degenerate Bose gas even at high temperatures. discuss this model context of recently discovered oxide superconductors.
We study a spin $S$ quantum Heisenberg model on the Fe lattice of rare-earth oxypnictide superconductors. Using both large and $N$ methods, we show that this exhibits sequence two phase transitions: from high-temperature symmetric to narrow region intermediate ``nematic'' phase, then low-temperature ordered phase. Identifying phases by their broken symmetries, these correspond precisely structural (tetragonal monoclinic) magnetic transitions have been recently revealed in neutron-scattering...
When holes are doped into an antiferromagnetic insulator they form a slowly fluctuating array of ``topological defects'' (metallic stripes) in which the motion exhibits self-organized quasi-one-dimensional electronic character. The accompanying lateral confinement intervening Mott-insulating regions induces spin gap or pseudogap environment stripes. We present theory underdoped high-temperature superconductors and show that there is local separation charge mobile on individual stripe acquire...
We introduce a model of the superconducting transition in bad metal, and show that quantum classical phase fluctuations prevent long-range order unless resistivity $\ensuremath{\rho}(T)$ falls below critical value. Application these ideas to high temperature superconductors accounts for variation $\ensuremath{\rho}({T}_{c})$ radiation-damaged films; gives an upper bound on ${T}_{c}\ensuremath{\propto}{n}_{s}$, where ${n}_{s}$ is zero-temperature superfluid density; shows that, with...
We report recent progress in determining the global behavior of two-dimensional electron gas a high magnetic field. Specifically, we have: (i) derived law corresponding states which allows us to construct phase diagram and calculate many interrelations between transport coefficients; (ii) ``selection rule'' governing allowed continuous transitions pairs quantum Hall liquid states; (iii) identified ``insulating state,'' have named insulator, as state which, temperature...
Abelian bosonization is used to map the two-channel Kondo problem into a resonant-level Hamiltonian, which equivalent noninteracting fermions for particular value of longitudinal exchange coupling. This solvable point analogous Toulouse limit ordinary problem. The impurity Green's function, susceptibility, and thermodynamic properties, together with certain conduction-electron correlation functions, are evaluated at point. In particular, it shown that pairing resonance may be characterized...
We develop a microscopic theory of the electronic nematic phase proximate to an isotropic Fermi liquid in both two and three dimensions. Explicit expressions are obtained for small amplitude collective excitations ordered state; remarkably, Goldstone mode (the director wave) is overdamped except along special directions dictated by symmetry. At quantum critical point we find dynamical exponent $z=3,$ implying stability Gaussian fixed point. The leading perturbative effect modes leads...
We investigate the stability of a quadratic band-crossing point (QBCP) in 2D fermionic systems. At noninteracting level, we show that QBCP exists and is topologically stable for Berry flux +/-2pi if symmetry group has either fourfold or sixfold rotational symmetries. This putative free-fermion marginally unstable to arbitrarily weak short-range repulsive interactions. consider both spinless spin-1/2 fermions. Four possible ordered states result: quantum anomalous Hall phase, spin nematic...
The polar Kerr effect in the high-${T}_{c}$ superconductor ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6+x}$ was measured at zero magnetic field with high precision using a cyogenic Sagnac fiber interferometer. We observed nonzero rotations of order $\ensuremath{\sim}1\text{ }\text{ }\ensuremath{\mu}\mathrm{rad}$ appearing near pseudogap temperature ${T}^{*}$ and marking what appears to be true phase transition. Anomalous behavior magnetic-field training suggests that time reversal...
Correlated electron fluids can exhibit a startling array of complex phases, among which one the more surprising is nematic, translationally invariant metallic phase with spontaneously generated spatial anisotropy. Classical nematics generally occur in liquids rod-like molecules; given that electrons are point like, initial theoretical motivation for contemplating came from thinking fluid as quantum melted crystal, rather than strongly interacting descendent Fermi gas. Dramatic transport...
We review the physics of pair density wave (PDW) superconductors. begin with a macroscopic description that emphasizes order induced by PDW states, such as charge wave, and discuss related vestigial states emerge consequence partial meting order. critically mounting experimental evidence for in cuprate superconductors, status theoretical microscopic order, current debate on whether is "mother order" or another competing cuprates. In addition, we give an overview weak coupling version...
We establish the existence of a chiral spin liquid (CSL) as exact ground state Kitaev model on decorated honeycomb lattice, which is obtained by replacing each site in familiar lattice with triangle. This CSL spontaneously breaks time reversal symmetry but preserves other symmetries. There are two topologically distinct CSL's separated quantum critical point. Interestingly, vortex excitations nontrivial (Chern number +/-1) obey non-Abelian statistics.
Charge density wave (CDW) correlations have recently been shown to universally exist in cuprate superconductors. However, their nature at high fields inferred from nuclear magnetic resonance is distinct that measured by x-ray scattering zero and low fields. Here we combine a pulsed magnet with an free electron laser characterize the CDW YBa2Cu3O6.67 via up 28 Tesla. While zero-field order, which develops below T ~ 150 K, essentially two-dimensional, lower temperature beyond 15 Tesla, another...
In this supporting material for the main paper (the preceding submission), we show, in addition to related information experiments, additional discussion that cannot fit (due space constraint). It includes further about our experimental observations, wider implications of findings with various reported candidates pseudogap order, and a simple mean-field argument favors interpretations based on finite-Q order (density wave) seen by ARPES (whether "the order" is single or contains multiple...