A5054169219- Topological Materials and Phenomena
- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Quantum many-body systems
- Quantum and electron transport phenomena
- Graphene research and applications
- Cold Atom Physics and Bose-Einstein Condensates
- Superconducting Materials and Applications
- Theoretical and Computational Physics
- Magnetic and transport properties of perovskites and related materials
- 2D Materials and Applications
- Quantum, superfluid, helium dynamics
- Atomic and Subatomic Physics Research
- Quantum Mechanics and Non-Hermitian Physics
- Superconductivity in MgB2 and Alloys
- Quantum Computing Algorithms and Architecture
- Quantum optics and atomic interactions
- Magnetic properties of thin films
- Iron-based superconductors research
- Inorganic Fluorides and Related Compounds
- Black Holes and Theoretical Physics
- Photorefractive and Nonlinear Optics
- Spectral Theory in Mathematical Physics
- Quantum chaos and dynamical systems
- Quantum Information and Cryptography
University of British Columbia
2016-2025
University of California, Santa Barbara
2001-2020
Universidad Braulio Carrillo
2002
Johns Hopkins University
1997-2001
Canadian Institute for Advanced Research
1997
McMaster University
1995-1996
Brockhouse Institute for Materials Research
1996
University of Rochester
1993-1995
Comenius University Bratislava
1989-1990
Ettore Majorana (1906-1938) disappeared while traveling by ship from Palermo to Naples in 1938. His fate has never been fully resolved and several articles have written that explore the mystery itself. demise intrigues us still today because of his seminal work, published previous year, established symmetric solutions Dirac equation describe a fermionic particle is its own anti-particle. This work long had significant impact neutrino physics, where this fundamental question regarding remains...
Itinerant electrons in a two-dimensional kagome lattice form Dirac semimetal, similar to graphene. When and spin symmetries are broken by various periodic perturbations this semimetal is shown spawn interesting nonmagnetic insulating phases. These include topological insulator with nontrivial ${\text{Z}}_{2}$ invariant robust gapless edge states, as well dimerized trimerized ``Kekul\'e'' insulators. The latter two topologically trivial but the Kekul\'e phase possesses complex order parameter...
It has been suggested recently, based on subtle field-theoretical considerations, that the electromagnetic response of Weyl semimetals and closely related insulators can be characterized by an axion term θE·B with space time dependent angle θ(r,t). Here we construct a minimal lattice model medium study its combination analytical numerical techniques. We confirm existence anomalous Hall effect expected basis field theory treatment. find, contrary to latter, chiral magnetic (that is, ground...
When a ferromagnet is deposited on the surface of topological insulator topologically protected state develops gap and becomes two-dimensional quantum Hall liquid. We demonstrate that current in such liquid, induced by an external electric field, can have dramatic effect magnetization dynamics changing effective anisotropy field. This change dissipationless may be substantial even weakly spin-orbit coupled ferromagnets. study possibility current-induced reversal monolayer-thin, insulating...
Two-dimensional topological insulators are hard to find. This theoretical paper by a group of physicists from Canada and US revives graphene as viable candidate for engineering robust, accessible two-dimensional insulators.
Most physical systems known to date tend resist entering the topological phase and must be fine-tuned reach that phase. Here, we introduce a system in which key dynamical parameter adjusts itself response changing external conditions so ground state naturally favors The consists of quantum wire formed individual magnetic atoms placed on surface an ordinary $s$-wave superconductor. It realizes Kitaev paradigm superconductivity when wave vector characterizing emergent spin helix dynamically...
Electrons hopping on the sites of a two-dimensional Lieb lattice and three-dimensional edge-centered cubic (perovskite) are shown to form topologically nontrivial insulating phases when spin-orbit coupling is introduced. These simple models lattices with symmetry show Dirac-type structure in excitation spectrum but unusual feature that there dispersionless band through center only single Dirac cone per Brillouin zone.
A topological insulator nanowire, proximity-coupled to an ordinary bulk s-wave superconductor and subject a longitudinal applied magnetic field, is shown realize one-dimensional with unpaired Majorana fermions localized at both ends. This situation occurs under wide range of conditions constitutes what possibly the most easily accessible physical realization elusive particles in solid-state system.
Dirac and Weyl semimetals form an ideal platform for testing ideas developed in high energy physics to describe massless relativistic particles. One such quintessentially field-theoretic idea of chiral anomaly already resulted the prediction subsequent observation pronounced negative magnetoresistance these novel materials parallel electric magnetic fields. Here we predict that occurs - has experimentally observable consequences when real electromagnetic fields E B are replaced by...
Twisted interfaces between stacked van der Waals (vdW) cuprate crystals present a platform for engineering superconducting order parameters by adjusting stacking angles. Using cryogenic assembly technique, we construct twisted vdW Josephson junctions (JJs) at atomically sharp Bi2Sr2CaCu2O8+x crystals, with quality approaching the limit set intrinsic JJs. Near 45° twist angle, observe fractional Shapiro steps and Fraunhofer patterns, consistent existence of two degenerate ground states...
Quantum computers hold the promise of solving certain problems that lie beyond reach conventional computers. Establishing this capability, especially for impactful and meaningful problems, remains a central challenge. Here we show superconducting quantum annealing processors can rapidly generate samples in close agreement with solutions Schrödinger equation. We demonstrate area-law scaling entanglement model quench dynamics two-, three- infinite-dimensional spin glasses, supporting observed...
An odd number of gapless Dirac fermions is guaranteed to exist at a surface strong topological insulator. We show that in thin-film geometry and under external bias, electron-hole pairs reside these states can condense form novel exotic quantum state which we propose call "topological exciton condensate" (TEC). This TEC similar general terms the condensate recently argued biased graphene bilayer, but with different properties. It exhibits host unusual properties including stable zero mode...
Within the phase fluctuation model for pseudogap state of cuprate superconductors we identify a novel statistical "Berry phase" interaction between nodal quasiparticles and fluctuating vortex-antivortex excitations. The effective action describing this assumes form an anisotropic Euclidean quantum electrodynamics in (2+1) dimensions (QED (3)) naturally generates non-Fermi liquid behavior its fermionic doping axis x -T diagram emerges as critical line which regulates low energy fermiology.
High-$T_c$ cuprates differ from conventional superconductors in three crucial aspects: the superconducting state descends a strongly correlated Mott-Hubbard insulator, order parameter exhibits d-wave symmetry and fluctuations play an all important role. We formulate theory of pseudogap by taking advantage these unusual features. The effective low energy within phase is shown to be equivalent (anisotropic) quantum electrodynamics (2+1) space-time dimensions (QED$_3$). role Dirac fermions...
Two-dimensional topological insulators (2D TIs) have been proposed as platforms for many intriguing applications, ranging from spintronics to quantum information processing. Realizing this potential will likely be facilitated by the discovery of new, easily manufactured materials in class. With goal mind, we introduce a new framework engineering 2D TI hybridizing graphene with impurity bands arising heavy adatoms possessing partially filled d shells, particular, osmium and iridium....
We show that disorder, when sufficiently strong, can transform an ordinary metal with strong spin-orbit coupling into a topological "Anderson" insulator, new phase of quantum matter in three dimensions characterized by disordered insulating bulk and topologically protected conducting surface states.
We consider the effect of classical phase fluctuations on quasiparticle spectra underdoped high-${T}_{c}$ cuprate superconductors in pseudogap regime above ${T}_{c}.$ show that photoemission and tunneling spectroscopy data are well accounted for by a simple model which mean-field $d$-wave quasiparticles semiclassically coupled to supercurrents induced fluctuating unbound vortex-antivortex pairs. argue imply transverse important at temperatures ${T}_{c},$ while longitudinal unimportant all...
We investigate quasiparticle states associated with an isolated vortex in a $d$-wave superconductor using self-consistent Bogoliubov--de Gennes formalism. For pure ${d}_{{x}^{2}{\ensuremath{-}y}^{2}}$ we find that there exist no bound the core; all are extended continuous energy spectrum. This result is inconsistent existing experimental data on cuprates. propose explanation for this terms of magnetic-field-induced ${d}_{{x}^{2}{\ensuremath{-}y}^{2}}{+id}_{\mathrm{xy}}$ state recently...
We show that a strongly interacting chain of Majorana zero modes exhibits supersymmetric quantum critical point corresponding to the c=7/10 tricritical Ising model, which separates phase in universality class from massive phase. verify our predictions with numerical density-matrix-renormalization-group computations and determine consequences for tunneling experiments.
Electrons hopping on the sites of a three-dimensional pyrochlore lattice are shown to form topologically non-trivial insulating phases when spin-orbit (SO) coupling and distortions present. Of 16 possible topological classes 9 realized for various parameters in this model. Specifically, at half-filling undistorted with SO term yields 'pristine' strong insulator Z2 index (1;000). At quarter filling weak obtained provided that both uniaxial distortion Our analysis suggests many non-magnetic...
We explore the possible particle-hole instabilities that can arise in a system of massless Dirac fermions on both honeycomb and pi-flux square lattices with short range interactions. Through analytical numerical studies we show these result number interesting phases. In addition to previously identified charge spin density wave phases exotic `quantum anomalous Hall' (Haldane) phase, establish existence dimerized Kekule phase over significant portion diagram discuss possibility its spinful...
It has been noted a long time ago that term of the form theta (e^2/2\pi h) B dot E may be added to standard Maxwell Lagrangian without modifying familiar laws electricity and magnetism. is known particle physicists as 'axion' field whether or not it nonzero expectation value in vacuum remains fundamental open question Standard Model. A key manifestation axion Witten effect: unit magnetic monopole placed inside medium with non-zero predicted bind (generally fractional) electric charge...
Topological phases of fermions in two dimensions are often characterized by chiral edge states. By definition, these propagate opposite directions at the parallel edges when sample geometry is that a rectangular strip. We introduce here model which exhibits what we call "antichiral" modes. These same direction both strip and compensated counterpropagating modes reside bulk. General arguments numerical simulations show backscattering suppressed even strong disorder present system. propose...