A5054264525- Rare-earth and actinide compounds
- Physics of Superconductivity and Magnetism
- Iron-based superconductors research
- Quantum and electron transport phenomena
- Advanced Condensed Matter Physics
- Topological Materials and Phenomena
- Magnetic and transport properties of perovskites and related materials
- Cold Atom Physics and Bose-Einstein Condensates
- Theoretical and Computational Physics
- Advanced Chemical Physics Studies
- Quantum, superfluid, helium dynamics
- High-pressure geophysics and materials
- Surface and Thin Film Phenomena
- Corporate Taxation and Avoidance
- Quantum many-body systems
- Magnetic Properties of Alloys
- Graphene research and applications
- Quantum chaos and dynamical systems
- Magnetic properties of thin films
- Advanced Materials Characterization Techniques
- Intellectual Capital and Performance Analysis
- Inorganic Chemistry and Materials
- Spectral Theory in Mathematical Physics
- Advanced Thermodynamics and Statistical Mechanics
- Quantum Information and Cryptography
Rice University
2016-2025
Astronomy and Space
2023
Zhejiang University
2020-2023
ORCID
2021
Institute of Modern Physics
2020
National Laboratory for Superconductivity
2014-2017
Institute of Physics
2014-2017
Chinese Academy of Sciences
2014-2017
Karlsruhe Institute of Technology
2011
Rutgers, The State University of New Jersey
1992-2007
We consider the iron pnictides in terms of a proximity to Mott insulator. The superexchange interactions contain competing nearest-neighbor and next-nearest-neighbor components. In undoped parent compound, these frustrated lead two-sublattice collinear antiferromagnet (each sublattice forming Néel ordering), with reduced magnitude for ordered moment. Electron or hole doping, together frustration effect, suppresses magnetic ordering allows superconducting state. exchange favor d-wave order...
Quantum phase transitions arise in many-body systems because of competing interactions that promote rivaling ground states. Recent years have seen the identification continuous quantum transitions, or critical points, a host antiferromagnetic heavy-fermion compounds. Studies interplay between various effects revealed new classes points and are uncovering plethora phases. At same time, criticality has provided fresh insights into electronic, magnetic, superconducting properties metals. We...
Using angle-resolved photoemission spectroscopy, we observe the low-temperature state of A(x)Fe(2-y)Se(2) (A=K, Rb) superconductors to exhibit an orbital-dependent renormalization bands near Fermi level-the d(xy) heavily renormalized compared d(xz)/d(yz) bands. Upon raising temperature above 150 K, system evolves into a in which have depleted spectral weight while remain metallic. Combined with theoretical calculations, our observations can be consistently understood as temperature-induced...
Establishing the appropriate theoretical framework for unconventional superconductivity in iron-based materials requires correct understanding of both electron correlation strength and role Fermi surfaces. This fundamental issue becomes especially relevant with discovery iron chalcogenide superconductors. Here, we use angle-resolved photoemission spectroscopy to measure three representative chalcogenides, FeTe0.56Se0.44, monolayer FeSe grown on SrTiO3 K0.76Fe1.72Se2. We show that these...
Nontrivial topology in condensed matter systems enriches quantum states of matter, to go beyond either the classification into metals and insulators terms conventional band theory or that symmetry broken phases by Landau's order parameter framework. So far, focus has been on weakly interacting systems, little is known about limit strong electron correlations. Heavy fermion are a highly versatile platform explore this regime. Here we report discovery giant spontaneous Hall effect Kondo...
Kagome materials often host exotic quantum phases, including spin liquids, Chern gap, charge order, and superconductivity. Existing scanning microscopy studies of the kagome order have been limited to non-kagome surface layers. Here we tunnel into lattice FeGe uncover features order. Our spectroscopic imaging identifes a 2x2 in magnetic lattice, resembling that discovered superconductors. Spin-mapping across steps unit-cell-height demonstrates this emerges from spin-polarized electrons with...
Motivated by the recent discovery of superconductivity in ${\mathrm{La}}_{3}{\mathrm{Ni}}_{2}{\mathrm{O}}_{7}$ under pressure, we discuss basic ingredients a model that captures its microscopic physics pressure tuning. We anchor our description terms spectroscopic evidence strong correlations this system. In bilayer Hubbard including Ni $3d$ ${x}^{2}\ensuremath{-}{y}^{2}$ and ${z}^{2}$ orbitals, show ground state crosses over from low-spin $S=1/2$ to high-spin $S=3/2$ state. state, two...
We discuss non-Fermi liquid and quantum critical behavior in heavy fermion materials, focussing on the mechanism by which electron mass appears to diverge at point. ask whether basic for transformation involves diffraction off a spin density wave, or break-down composite nature of takes place show that Hall constant changes continously first scenario, but may ``jump'' discontinuously point where character quasiparticles changes.
At a generic quantum critical point, the thermal expansion alpha is more singular than specific heat c(p). Consequently, "Grüneisen ratio," Gamma=alpha/c(p), diverges. When scaling applies, Gamma approximately T(-1/(nu z)) at pressure p=p(c), providing means to measure dimension of most relevant operator that couples to; in alternative limit T-->0 and p not equal p(c), 1/(p-p(c)) with prefactor is, up molar volume, simple universal combination exponents. For magnetic-field driven transition,...
Neutron experiments have indicated that the structure factor S(q,\ensuremath{\omega}) for two cuprates ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ and ${\mathrm{La}}_{2\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_{4}$ has a different q dependence. Commensurate peaks at (\ensuremath{\pi}/a,\ensuremath{\pi}/a) are observed in former case, whereas clearly incommensurate seen latter, metallic hole...
We report thermodynamic measurements in a magnetic-field-driven quantum critical point of heavy fermion metal, YbRh$_2$Si$_2$. The data provide evidence for an energy scale the equilibrium excitation spectrum, that is addition to one expected from slow fluctuations order parameter. Both scales approach zero as reached, thereby providing new class criticality.
We present low-temperature volume thermal expansion, beta, and specific heat, C, measurements on high-quality single crystals of CeNi2Ge2 YbRh2(Si0.95Ge0.05)(2) which are located very near to quantum critical points. For both systems, beta shows a more singular temperature dependence than thus the Grüneisen ratio Gamma proportional beta/C diverges as T-->0. CeNi2Ge2, our results in accordance with spin-density wave (SDW) scenario for three-dimensional spin fluctuations. By contrast, observed...
We study the competition between intersite and local correlations in a spinless two-band extended Hubbard model by taking an alternative limit of infinite dimensions. find that density fluctuations suppress charge Kondo energy scale lead to Fermi liquid non-Fermi-liquid transition for repulsive on-site density-density interactions. In absence interactions, this reduces known Kosterlitz-Thouless transition. show new line fixed points replace those zero interaction problem.
Understanding the microscopic origins of electronic phases in high-transition temperature (high-Tc) superconductors is important for elucidating mechanism superconductivity. In paramagnetic tetragonal phase BaFe2-xTxAs2 (where T Co or Ni) iron pnictides, an in-plane resistivity anisotropy has been observed. Here we use inelastic neutron scattering to show that low-energy spin excitations these materials change from four-fold symmetric two-fold at temperatures corresponding onset anisotropy....
Two major themes in the physics of condensed matter are quantum critical phenomena and unconventional superconductivity. These usually occur context competing interactions systems strongly correlated electrons. All this interesting comes together behavior recently discovered iron pnictide compounds that have generated enormous interest because their moderately high-temperature The ubiquity antiferromagnetic ordering phase diagrams naturally raises question relevance magnetic criticality, but...
We study a multiorbital model for the alkaline iron selenides K(1-x)Fe(2-y)Se(2) using slave-spin method. With or without ordered vacancies, we identify metal-to-Mott-insulator transition at commensurate filling of six 3d electrons per ion. For Hund's couplings beyond threshold value, this occurs via an intermediate orbital-selective Mott phase, in which xy orbital is localized while other orbitals remain itinerant. This phase still stabilized over range carrier dopings. Our results lead to...
We study a holographic model realizing an ``antiferromagnetic'' phase in which global $SU(2)$ symmetry representing spin is broken down to $U(1)$ by the presence of finite electric charge density. This involves condensation neutral scalar field charged anti--de Sitter black hole. observe that transition for both and (as standard superconductor) order parameters can be driven zero temperature tuning UV conformal dimension parameter, resulting quantum Berezinskii-Kosterlitz-Thouless--type....