A5026496541- Topological Materials and Phenomena
- Physics of Superconductivity and Magnetism
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced Condensed Matter Physics
- Quantum and electron transport phenomena
- Rare-earth and actinide compounds
- Quantum, superfluid, helium dynamics
- Magnetic properties of thin films
- Iron-based superconductors research
- High-pressure geophysics and materials
- Quantum many-body systems
- Graphene research and applications
- Diamond and Carbon-based Materials Research
- Photorefractive and Nonlinear Optics
- Atomic and Subatomic Physics Research
- Quantum optics and atomic interactions
- Corporate Taxation and Avoidance
- Algebraic structures and combinatorial models
- Advanced Materials Characterization Techniques
- Magnetic Properties of Alloys
- Phase-change materials and chalcogenides
- Nuclear materials and radiation effects
- Transportation Systems and Logistics
- Magnetic Properties and Synthesis of Ferrites
- Advanced Frequency and Time Standards
George Mason University
2011-2024
Johns Hopkins University
2012-2024
Argonne National Laboratory
2011
National Institute of Standards and Technology
2010
Rice University
2009-2010
Harvard University
2006-2007
Massachusetts Institute of Technology
2003-2005
Vodovod-Kanalizacija (Slovenia)
2005
University of Belgrade
1999
Institute of Physics Belgrade
1985
We lay out an experiment to realize time-reversal invariant topological insulators in alkali atomic gases. introduce original method synthesize a gauge field the near-field of atom-chip, which effectively mimics effects spin-orbit coupling and produces quantum spin-Hall states. also propose feasible scheme engineer sharp boundaries where hallmark edge states are localized. Our multi-band system has large parameter space exhibiting variety phase transitions between normal insulating phases....
It has long been known that particles with short-range repulsive interactions in spatial dimension d=1 form universal quantum liquids the low density limit: all properties can be related to those of spinless free Fermi gas. Previous renormalization group (RG) analyses demonstrated this universality is described by an RG fixed point, infrared stable for d<2, zero We show d>2 same point describes attractive near a Feshbach resonance; now unstable, and relevant perturbation detuning resonance....
Using inelastic neutron scattering, we map a 14 meV coherent resonant mode in the topological Kondo insulator ${\mathrm{SmB}}_{6}$ and describe its relation to low energy insulating band structure. The intensity is confined $X$ $R$ high symmetry points, repeating outside first Brillouin zone dispersing less than 2 meV, with $5d$-like magnetic form factor. We present slave-boson treatment of Anderson Hamiltonian third neighbor dominated hybridized This approach produces spin exciton below...
This paper is concerned with physics of the low energy singlet excitations found to exist below spin gap in numerical studies Kagome lattice quantum Heisenberg antiferromagnet. Insight into nature these obtained by exploiting an approximate mapping a fully frustrated transverse field Ising model on dual dice lattice. shown possess at least two phases - ordered phase that also breaks translational symmetry large unit cell, and paramagnetic phase. The former argued be likely candidate for...
Weyl electrons are intensely studied due to novel charge transport phenomena such as chiral anomaly, Fermi arcs, and photogalvanic effect. Recent theoretical works suggest that can also participate in magnetic interactions, the Weyl-mediated indirect exchange coupling between local moments is proposed a new mechanism of spiral magnetism involves electrons. Despite reports incommensurate non-collinear ordering semimetals, an actual order has remained hitherto undetected. Here, we present...
Nonlinear helicity-dependent photocurrents have been reported in 3D topological materials lacking inversion symmetry. Here, we theoretically study the charge and spin generated by linear circularly polarized radiation ultrathin insulator films. Using time-dependent perturbation theory detailed balance equations, find that helical transverse currents are when symmetry between top bottom film surfaces is disturbed. Such invariant under in-plane mirror transformations but $s$-wave $d$-wave...
Samarium hexaboride (SmB6) is a Kondo insulator, with narrow gap due to hybridization between localized and conduction electrons. Despite being an many samples show metal-like properties. Rare-earth purification exceedingly difficult, nominally pure may contain 2% or more of impurities. Here determine the effects rare-earth doping on SmB6, we synthesized probed series gadolinium-doped samples. We found relationship specific heat impurity moment screening which scales systematically....
We explore the stability of certain many-body quantum states which may exist at zero or finite temperatures, lack long-range order and even topological order, still are thermodynamically distinct from uncorrelated disordered phases. sharply characterize such by conservation charge, equivalently confinement instantons, using a generalization Wilson loop correlation length an emergent gauge field. Our main conclusions (i) orders can (ii) relativistic liquids defects also as stable phases (iii)...
We consider spin-1/2 fermions of mass m with interactions near the unitary limit. In an applied periodic potential amplitude V and period a, a density even integer number per unit cell, there is second-order quantum phase transition between superfluid insulating ground states at critical V=Vc. compute universal ratio Vc a^2 / h^2 N=infinity in model Sp(2N) spin symmetry. The insulator interpolates band Mott fermion pairs. discuss implications for recent experiments.
Samarium hexaboride $({\mathrm{SmB}}_{6})$, a representative Kondo insulator, has been characterized recently as likely topological insulator. It is also material with strong electron correlations, evident by the temperature dependence of its band gap and existence nearly flat collective mode whose energy lies within gap. Similar correlations can affect or even destabilize two-dimensional metallic state origin at crystal boundary. Here we construct minimal lattice model correlated boundary...
Samarium hexaboride (SmB$_6$) is the first strongly correlated material with a recognized non-trivial band-structure topology. Its electron correlations are seen by inelastic neutron scattering as coherent collective excitation at energy of 14 meV. Here we calculate spectrum this mode using perturbative slave boson method. Our starting point recently constructed Anderson model that properly captures topology SmB$_6$. Most self-consistent renormalization effects captured few phenomenological...
We derive the effective interactions between local magnetic moments which are mediated by Weyl electrons in topological semimetals. The resulting spin dynamics is governed induced Heisenberg, Kitaev, and Dzyaloshinskii-Moriya (DM) with extended range oscillatory dependence on distance spins. These realized multiple competing channels shaped multitude of nodes electron spectrum. Microscopic spins need to be spatially modulated a channel-dependent wave vector order take advantage interactions....
We study the quantum Ising antiferromagnet on kagome lattice, with weak transverse field dynamics and other local perturbations. analytically demonstrate possibility of a disordered zero-temperature phase that is smoothly connected to at strong fields. This done by means an appropriate mapping compact U(1) gauge theory honeycomb lattice coupled charge-1 matter field. Our results are consistent existing Monte-Carlo calculations. The differences commonly studied models two-dimensional lattices...
We develop a field theory of quantum magnets and magnetic (semi)metals, which is suitable for the analysis their universal topological properties. The systems interest include collinear, coplanar, general noncoplanar magnets. At basic level, we describe dynamics moments using smooth vector fields in continuum limit. Dzyaloshinskii-Moriya interaction captured by non-Abelian gauge field, chiral spin couplings related to defects appear as higher-rank antisymmetric tensor fields. distinguish...
We describe the influence of gapless, nodal, fermionic quasiparticles a two-dimensional $d$-wave superconductor on motion vortices. A continuum, functional formalism is used to obtain effective vortex action, after fermions have been integrated out. At zero temperature $(T)$, leading terms in action retain their original form, with only an infrared finite renormalization mass from fermions. universal ``sub-Ohmic'' damping also found. $T>0$, we find Bardeen-Stephen viscous drag term,...
Motivated by the bad metal behavior of iron pnictides, we study a multi-orbital $\mathrm{t-J_1-J_2}$ model and investigate possible singlet superconducting pairings. Magnetic frustration itself leads to large degeneracy in pairing states. The kinetic energy breaks this into quasi-degeneracy among reduced set For small electron hole Fermi pockets, an $A_{1g}$ state dominates over phase diagram but $B_{1g}$ has close-by energy. In addition nodeless $s_{x^2y^2}$ channel, nodal $s_{x^2+y^2}$...
The pseudogap state of cuprate high-temperature superconductors has been often viewed as either a yet unknown competing order or precursor to superconductivity. While awaiting the resolution problem in cuprates, we demonstrate that local pairing fluctuations, vortex liquid dynamics, and other phenomena can emerge quite generally whenever fermionic excitations remain gapped across superconducting transition, regardless gap origin. Our choice tractable model is lattice band insulator with...
Certain insulating materials with strong spin-orbit interaction can conduct currents along their edges or surfaces owing to the nontrivial topological properties of electronic band structure. This phenomenon is somewhat similar integer quantum Hall effect electrons in magnetic fields. Topological insulators analogous fractional are also possible, but have not yet been observed any material. Here we show that a well made from insulator such as ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$...
We use quantum Monte Carlo and exact diagonalization calculations to study the Mott-insulator superconductor phase transition in a two-dimensional fermionic Hubbard model with attractive interactions presence of superlattice potential. The introduced offers unique possibilities such transitions optical lattice experiments. show that, regimes moderate strong interactions, belongs 3D-XY universality class. also explore character lowest energy charge excitations insulating superconducting...
Impurities and defects in Kondo insulators can have an unusual impact on dynamics that blends with effects of intrinsic electron correlations. Such crystal imperfections are difficult to avoid, their consequences incompletely understood. Here we study magnetic impurities via perturbation theory the s-d impurity model adapted small bandgap insulators. The calculated magnetization specific heat agree recent thermodynamic measurements samarium hexaboride (SmB$_6$). This qualitative agreement...
A many-body quantum system whose topological defects are conserved, abundant, and mobile is a correlated liquid. Since can be classified by homotopy groups, each identifies class of liquids. Here we explore the liquids based on ${\ensuremath{\pi}}_{3}({S}^{2})$ group, i.e., Hopf fibration. Their topologically nontrivial dynamics emerges from interlinking between magnetic flux or skyrmion loops in charge spin sectors respectively. We lay down field theory foundation for analyzing such states...
We study multigap superconductivity, with strong angular variations of one the gaps, as appropriate for certain iron-based high-temperature superconductors. solve gap equations this model and find that nodes or zeroes in function present at Tc - although purely accidental -- typically survive down to T=0. Based on result, we investigate line quantum transitions which first appear. The peculiar "zero-point" critical scaling emanating from dominates quasiparticle thermodynamics transport...