Publications (55)231.45 Total impact
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ABSTRACT: In contrast to conventional swave superconductivity, unconventional (e.g. p or dwave) superconductivity is strongly suppressed even by relatively weak disorder. Upon approaching the superconductormetal transition, the order parameter amplitude becomes increasingly inhomogeneous leading to effective granularity and a phase ordering transition described by the Mattis model of spin glasses. One consequence of this is that at low enough temperatures, between the clean unconventional superconducting and the diffusive metallic phases, there is necessarily an intermediate superconducting phase which exhibits swave symmetry on macroscopic scales.05/2014;  [Show abstract] [Hide abstract]
ABSTRACT: We study low temperature electron transport in pwave superconductorinsulatornormal metal junctions. In diffusive metals the pwave component of the order parameter decays exponentially at distances larger than the mean free path $l$. At the superconductornormal metal boundary, due to spinorbit interaction, there is a triplet to singlet conversion of the superconducting order parameter. The singlet component survives at distances much larger than $l$ from the boundary. It is this component that controls the low temperature resistance of the junctions. As a result, the resistance of the system strongly depends on the angle between the insulating boundary and the ${\bf d}$vector characterizing the spin structure of the triplet superconducting order parameter. We also analyze the spatial dependence of the electric potential in the presence of the current, and show that the electric field is suppressed in the insulating boundary as well as in the normal metal at distances of order of the coherence length away from the boundary. This is very different from the case of the normal metalinsulatornormal metal junctions, where the voltage drop takes place predominantly at the insulator.Physical Review B 10/2013; 89(1). · 3.66 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We study the structure of Bogoliubov quasiparticles, bogolons, the fermionic excitations of paired superfluids that arise from fermion (BCS) pairing, including neutral superfluids, superconductors, and paired quantum Hall states. The naive construction of a stationary quasiparticle in which the deformation of the pair field is neglected leads to a contradiction: it carries a net electrical current even though it does not move. However, treating the pair field selfconsistently resolves this problem: in a neutral superfluid, a dipolar current pattern is associated with the quasiparticle for which the total current vanishes. When Maxwell electrodynamics is included, as appropriate to a superconductor, this pattern is confined over a penetration depth. For paired quantum Hall states of composite fermions, the Maxwell term is replaced by a ChernSimons term, which leads to a dipolar charge distribution and consequently to a dipolar current pattern.Physical Review Letters 12/2012; 109(23):237004. · 7.73 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We consider the classical magnetoresistance of a Weyl metal in which the electron Fermi surface possess nonzero fluxes of the Berry curvature. Such a system may exhibit large negative magnetoresistance with unusual anisotropy as a function of the angle between the electric and magnetic fields. In this case the system can support a new type of plasma waves. These phenomena are consequences of chiral anomaly in electron transport theory.Physical review. B, Condensed matter 06/2012; 88(10). · 3.66 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Paired quantum Hall states such as the Pfaffian exhibit a weakcoupling regime much like that of BCS superconductivity. In this regime their lowest energy excitations are neutral fermions  Bogoliubov quasiparticles constructed from the composite fermions  and not the charged vortices which generally govern the behavior of quantum Hall states. We discuss a rich set of phenomena which follow from this observation. At finite temperatures of order the pairing scale these include (i) an almost sharp phase transition (ii) a new finitetemperature length scale for the penetration of longitudinal electric fields, and (iii) the existence of a new collective excitation in paired QH states which is a cousin to the well known ArtemenkoVolkovCarlsonGoldmanSchmidSchon mode in conventional superconductors. At lower temperatures, we find (i) a proximity effect between the paired states and their ancestor metals, which in turn mediates (ii) `Josephson' couplings between paired QH droplets separated by metallic regions and leads to (iii) a distinctive response of such states to disorder; and finally, we also comment on (iv) an analog of Andreev reflection in these systems.02/2012;  [Show abstract] [Hide abstract]
ABSTRACT: We study the structure of Bogoliubov quasiparticles, 'bogolons,' the fermionic excitations of paired superfluids that arise from fermion (BCS) pairing, including neutral superfluids, superconductors, and paired quantum Hall states. The naive construction of a stationary quasiparticle in which the deformation of the pair field is neglected leads to a contradiction: it carries a net electrical current even though it does not move. However, treating the pair field selfconsistently resolves this problem: In a neutral superfluid, a dipolar current pattern is associated with the quasiparticle for which the total current vanishes. When Maxwell electrodynamics is included, as appropriate to a superconductor, this pattern is confined over a penetration depth. For paired quantum Hall states of composite fermions, the Maxwell term is replaced by a ChernSimons term, which leads to a dipolar charge distribution and consequently to a dipolar current pattern.arxiv:1202.3444. 01/2012;  [Show abstract] [Hide abstract]
ABSTRACT: We introduce a new mechanism for the propulsion and separation by chirality of small ferromagnetic particles suspended in a liquid. Under the action of a uniform dc magnetic field H and an ac electric field E isomers with opposite chirality move in opposite directions. Such a mechanism could have a significant impact on a wide range of emerging technologies. The component of the chiral velocity that is odd in H is found to be proportional to the intrinsic orbital and spin angular momentum of the magnetized electrons. This effect arises because a ferromagnetic particle responds to the applied torque as a small gyroscope.Physical Review E 01/2012; 85(1 Pt 2):016321. · 2.31 Impact Factor 
Article: A Typology for Quantum Hall Liquids
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ABSTRACT: There is a close analogy between the response of a quantum Hall liquid (QHL) to a small change in the electron density and the response of a superconductor to an externally applied magnetic flux  an analogy which is made concrete in the ChernSimons LandauGinzburg (CSLG) formulation of the problem. As the Types of superconductor are distinguished by this response, so too for QHLs: a typology can be introduced which is, however, richer than that in superconductors owing to the lack of any timereversal symmetry relating positive and negative fluxes. At the boundary between Type I and Type II behavior, the CSLG action has a "Bogomol'nyi point," where the quasiholes (vortices) are noninteracting  at the microscopic level, this corresponds to the behavior of systems governed by a set of model Hamiltonians which have been constructed to render exact a large class of QHL wavefunctions. All Types of QHLs are capable of giving rise to quantized Hall plateaux.Physical review. B, Condensed matter 08/2011; · 3.66 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We develop a hydrodynamic description of the resistivity and magnetoresistance of an electron liquid in a smooth disorder potential. This approach is valid when the electronelectron scattering length is sufficiently short. In a broad range of temperatures, the dissipation is dominated by heat fluxes in the electron fluid, and the resistivity is inversely proportional to the thermal conductivity, κ. This is in striking contrast to the Stokes flow, in which the resistance is independent of κ and proportional to the fluid viscosity. We also identify a new hydrodynamic mechanism of spin magnetoresistance.Physical Review Letters 06/2011; 106(25):256804. · 7.73 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The Pfaffian phase in the proximity of a halffilled Landau level is understood to be a p+ip superconductor of composite fermions. We consider the properties of this paired quantum Hall phase when the pairing energy is small, i.e., in the weakcoupling, BCS limit, where the coherence length is much larger than the charge screening length. We find that, as in a type I superconductor, vortices attract so that, upon varying the magnetic field from its magic value at ν=5/2, the system exhibits Coulomb frustrated phase separation. We propose that the weakly and strongly coupled Pfaffians exemplify a general dichotomy between type I and type II quantum Hall fluids.Physical Review Letters 06/2011; 106(23):236801. · 7.73 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We obtain hydrodynamic equations describing a fluid consisting of chiral molecules or a suspension of chiral particles in a Newtonian fluid. The hydrodynamic velocity and stresses arising in a flowing chiral liquid have components that are forbidden by symmetry in a Newtonian liquid. For example, a chiral liquid in a Poiseuille flow between parallel plates exerts forces on the plates, which are perpendicular to the flow. A generic flow results in spatial separation of particles of different chirality. Thus even a racemic suspension will exhibit chiral properties in a generic flow. A suspension of particles of random shape in a Newtonian liquid is described by equations which are similar to those describing a racemic mixture of chiral particles in a liquid.Physical Review Letters 05/2010; 104(19):198301. · 7.73 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: An overview of the measured transport properties of the two dimensional electron fluids in high mobility semiconductor devices with low electron densities is presented as well as some of the theories that have been proposed to account for them. Many features of the observations are not easily reconciled with a description based on the well understood physics of weakly interacting quasiparticles in a disordered medium. Rather, they reflect new physics associated with strong correlation effects, which warrant further study.Review of Modern Physics 01/2010; 82:17431766. · 42.86 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We develop a semiclassical theory of nonlinear transport and the photogalvanic effect in noncentrosymmetric media. We show that terms in semiclassical kinetic equations for electron motion which are associated with the Berry curvature and side jumps give rise to a dc current quadratic in the amplitude of the ac electric field. We demonstrate that the circular photogalvanic effect is governed by these terms in contrast to the linear photogalvanic effect and nonlinear IV characteristics which are governed mainly by the skew scattering mechanism. In addition, the Berry curvature contribution to the magneticfield induced photogalvanic effect is calculated.05/2009;  [Show abstract] [Hide abstract]
ABSTRACT: We develop a theory of photoinduced drift of chiral molecules or small particles in classical buffer gases. In the absence of a magnetic field there exists a flux of chiral molecules, provided the electromagnetic field is circularly polarized. It has opposite signs for different chiral isomers. In the presence of a magnetic field the flux can be also induced by a linearly polarized (or unpolarized) electromagnetic field. The magnitude of the flux is not proportional to either linear or orbital momentum of the electromagnetic field.Physical Review Letters 03/2009; 102(6):063004. · 7.73 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We study suppression of superconductivity by disorder in dwave superconductors, and predict the existence of (at least) two sequential low temperature transitions as a function of increasing disorder: a d wave to wave, and then an swave to metal transition. This is a universal property of the system which is independent of the sign of the interaction constant in the schannelPhysica B Condensed Matter 10/2008; · 1.28 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We develop a theory of the conductance of superconductor/normal metal/superconductor junctions in the case where the superconducting order parameter has dwave symmetry. At low temperature the conductance is proportional to the square root of the inelastic electron relaxation time in the bulk of the superconductor. As a result it turns out to be much larger than the conductance of the normal part of the junction.Physical Review Letters 06/2008; 100(24):247004. · 7.73 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We derive the theory of the quantum (zero temperature) superconductor to metal transition in disordered materials when the resistance of the normal metal near criticality is small compared to the quantum of resistivity. This can occur most readily in situations in which ``Anderson's theorem'' does not apply. We explicitly study the transition in superconductormetal composites, in an swave superconducting film in the presence of a magnetic field, and in a low temperature disordered dwave superconductor. Near the point of the transition, the distribution of the superconducting order parameter is highly inhomogeneous. To describe this situation we employ a procedure which is similar to that introduced by Mott for description of the temperature dependence of the variable range hopping conduction. As the system approaches the point of the transition from the metal to the superconductor, the conductivity of the system diverges, and the WiedemannFranz law is violated. In the case of dwave (or other exotic) superconductors we predict the existence of (at least) two sequential transitions as a function of increasing disorder: a dwave to swave, and then an swave to metal transition.Physical review. B, Condensed matter 03/2008; · 3.66 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: It is shown that in bulk disordered superconductors there exist spatial mesoscopic fluctuations of the electrochemical potential which are proportional to the temperature gradient. The amplitude of these fluctuations, when measured by point contacts, does not depend on the separation between the contacts.EPL (Europhysics Letters) 07/2007; 8(7):669. · 2.27 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We show that at zero temperature the supercurrent through the superconductor–ferromagneticmetal–superconductor (SFS) junctions does not decay exponentially with the thickness L of the junction. At large L it has a random samplespecific sign which can change with a change in temperature. In the case of mesoscopic junctions the phase of the order parameter in the ground state is a random samplespecific quantity. In the case of junctions of large area the groundstate phase difference is ±π/2.EPL (Europhysics Letters) 01/2007; 62(1):97. · 2.27 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We develop a general method for calculating statistical properties of the speckle pattern of coherent waves propagating in disordered media. In some aspects this method is similar to the BoltzmannLangevin approach for the calculation of classical fluctuations. We apply the method to the case where the incident wave experiences many small angle scattering events during propagation, but the total angle change remains small. In many aspects our results for this case are different from results previously known in the literature. The correlation function of the wave intensity at two points separated by a distance r, has a longrange character. It decays as a power of r and changes sign. We also consider sensitivities of the speckles to changes of external parameters, such as the wave frequency and the incidence angle.Physical Review Letters 01/2007; 97(22):223901. · 7.73 Impact Factor
Publication Stats
1k  Citations  
231.45  Total Impact Points  
Top Journals
Institutions

2012

University of California, Berkeley
 Department of Physics
Berkeley, CA, United States


1994–2012

University of Washington Seattle
 • Department of Applied Mathematics
 • Department of Physics
Seattle, WA, United States


2011

Princeton University
 Department of Physics
Princeton, NJ, United States


2006

Stony Brook University
Stony Brook, New York, United States
