Results for "Matthew P. A. Fisher"

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Quantum Cognition: The possibility of processing with nuclear spins in the brainAug 19 2015Aug 29 2015The possibility that quantum processing with nuclear spins might be operative in the brain is proposed and then explored. Phosphorus is identified as the unique biological element with a nuclear spin that can serve as a qubit for such putative quantum ... More
Mott Insulators, Spin Liquids and Quantum Disordered SuperconductivityJun 12 1998Dec 11 1998These introductory lecture notes describe recent results on novel Mott insulating phases which are "descendents" of superconductors - obtained by "quantum disordering". After a brief overview of quantum magnetism, attention is focussed on the spin-liquid ... More
Cooper pair tunnelling into a Quantum Hall fluidNov 17 1993Transport through a tunnel junction connecting a superconductor to a spin-aligned quantum Hall fluid at filling $\nu$ is studied theoretically. The dominant transport channel at low temperatures is the tunnelling of Cooper pairs into edge states of the ... More
Non-linear Transport in Quantum-Hall SmecticsJan 03 2000Recent transport experiments have established that two-dimensional electron systems with high-index partial Landau level filling, $\nu^{*} =\nu - \lbrack \nu \rbrack$, have ground states with broken orientational symmetry. In a mean-field theory, the ... More
Quantum Theory of Quantum-Hall SmecticsJul 19 1999We propose a quantum stripe (smectic) coupled-Luttinger-liquid model for the anisotropic states which occur in two-dimensional electron systems with high-index partial Landau level filling, $\nu^{*} = \nu - \lbrack\nu\rbrack$. Perturbative renormalization ... More
Quantum Indistinguishability in Chemical ReactionsJul 17 2017Oct 04 2017Quantum indistinguishability plays a crucial role in many low-energy physical phenomena, from quantum fluids to molecular spectroscopy. It is, however, typically ignored in most high temperature processes, particularly for ionic coordinates, implicitly ... More
Exotic paired states with anisotropic spin-dependent Fermi surfacesMar 15 2009We propose a model for realizing exotic paired states in cold atomic Fermi gases. By using a {\it spin dependent} optical lattice it is possible to engineer spatially anisotropic Fermi surfaces for each hyperfine species, that are rotated 90 degrees with ... More
Interplay between lattice-scale physics and the quantum Hall effect in grapheneJun 26 2007Graphene's honeycomb lattice structure underlies much of the remarkable physics inherent in this material, most strikingly through the formation of two ``flavors'' of Dirac cones for each spin. In the quantum Hall regime, the resulting flavor degree of ... More
Critical spin liquid at 1/3 magnetization in a spin-1/2 triangular antiferromagnetSep 18 2006Feb 23 2007Although magnetically ordered at low temperatures, the spin-1/2 triangular antiferromagnet Cs_2CuCl_4 exhibits remarkable spin dynamics that strongly suggest proximity to a spin liquid phase. Here we address the question of whether a proximate spin liquid ... More
Quantum Confinement Transition and Cuprate CriticalityDec 21 1999Theoretical attempts to explain the origin of high temperature superconductivity are challenged by the complexity of the normal state, which exhibits three regimes with increasing hole doping: a pseudo-gap regime when underdoped, strange power laws near ... More
Transport in a one-dimensional Luttinger liquidOct 06 1996In this paper we review recent theoretical results for transport in a one-dimensional (1d) Luttinger liquid. For simplicity, we ignore electron spin, and focus exclusively on the case of a single-mode. Moreover, we consider only the effects of a single ... More
Line Junctions in the Quantum Hall EffectSep 18 1996A long skinny gate across a fractional quantum Hall fluid at filling $\nu=1/m$ with odd integer $m$, creates a novel one-dimensional (1d) system which is isomorphic to a disordered 1d electron gas with {\it attractive} interactions. By varying the gate ... More
Conductance fluctuations at the integer quantum Hall plateau transitionSep 04 1996Nov 13 1996We study numerically conductance fluctuations near the integer quantum Hall effect plateau transition. The system is presumed to be in a mesoscopic regime, with phase coherence length comparable to the system size. We focus on a two-terminal conductance ... More
Gapless layered three-dimensional fractional quantum Hall statesFeb 04 2009Jun 17 2009Using the parton construction, we build a three-dimensional (3D) multilayer fractional quantum Hall state with average filling \nu = 1/3 per layer that is qualitatively distinct from a stacking of weakly coupled Laughlin states. The state supports gapped ... More
The Partially-Split Hall Bar: Tunneling in the Bosonic Integer Quantum Hall EffectNov 01 2013Jul 23 2014We study point-contact tunneling in the integer quantum Hall state of bosons. This symmetry-protected topological state has electrical Hall conductivity equal to $2 e^2/h$ and vanishing thermal Hall conductivity. In contrast to the integer quantum Hall ... More
Exotic paired phases in ladders with spin-dependent hoppingJul 29 2010Fermions in two-dimensions (2D) when subject to anisotropic spin-dependent hopping can potentially give rise to unusual paired states in {\it unpolarized} mixtures that can behave as non-Fermi liquids. One possibility is a fully paired state with a gap ... More
D-wave correlated Critical Bose Liquids in two dimensionsMar 12 2007We develop a description of a new quantum liquid phase of interacting bosons in 2d which possesses relative D-wave two-body correlations and which we call a D-wave Bose Liquid (DBL). The DBL has no broken symmetries, supports gapless boson excitations ... More
Contacts and Edge State Equilibration in the Fractional Quantum Hall EffectJun 26 1995We develop a simple kinetic equation description of edge state dynamics in the fractional quantum Hall effect (FQHE), which allows us to examine in detail equilibration processes between multiple edge modes. As in the integer quantum Hall effect (IQHE), ... More
Bond algebraic liquid phase in strongly correlated multiflavor cold atom systemsNov 24 2006Dec 03 2006When cold atoms are trapped in a square or cubic optical lattice, it should be possible to pump the atoms into excited $p-$level orbitals within each well. Following earlier work, we explore the metastable equilibrium that can be established before the ... More
Competing orders, non-linear sigma models, and topological terms in quantum magnetsOct 18 2005A number of examples have demonstrated the failure of the Landau-Ginzburg-Wilson(LGW) paradigm in describing the competing phases and phase transitions of two dimensional quantum magnets. In this paper we argue that such magnets possess field theoretic ... More
The Roton Fermi LiquidJul 17 2003We introduce and analyze a novel metallic phase of two-dimensional (2d) electrons, the Roton Fermi Liquid (RFL), which, in contrast to the Landau Fermi liquid, supports both gapless fermionic and bosonic quasiparticle excitations. The RFL is accessed ... More
Fractionalization and confinement in the U(1) and $Z_2$ gauge theories of strongly correlated systemsJun 30 2000Recently, we have elucidated the physics of electron fractionalization in strongly interacting electron systems using a $Z_2$ gauge theory formulation. Here we discuss the connection with the earlier U(1) gauge theory approaches based on the slave boson ... More
Z_2 Gauge Theory of Electron Fractionalization in Strongly Correlated SystemsOct 15 1999Oct 21 1999We develop a new theoretical framework for describing and analyzing exotic phases of strongly correlated electrons which support excitations with fractional quantum numbers. Starting with a class of microscopic models believed to capture much of the essential ... More
Quasiparticle density of states in dirty high-T_c superconductorsOct 20 1998We study the density of quasiparticle states of dirty d-wave superconductors. We show the existence of singular corrections to the density of states due to quantum interference effects. We then argue that the density of states actually vanishes in the ... More
Quantized Thermal Transport in the Fractional Quantum Hall EffectMar 15 1996We analyze thermal transport in the fractional quantum Hall effect (FQHE), employing a Luttinger liquid model of edge states. Impurity mediated inter-channel scattering events are incorporated in a hydrodynamic description of heat and charge transport. ... More
Chiral Surface States in the Bulk Quantum Hall EffectOct 16 1995In layered samples which exhibit a bulk quantum Hall effect (QHE), a two-dimensional (2d) surface ``sheath" of gapless excitations is expected. These excitations comprise a novel 2d chiral quantum liquid which should dominate the low temperature transport ... More
Critical Dynamics of Thermal Conductivity at the Normal-Superconducting TransitionDec 27 2000We study the effect of thermal fluctuations on the critical dynamics of the three-dimensional disordered superconductor across the normal-superconducting transition. We employ a phenomenological hydrodynamic approach, and in particular find the thermal ... More
Quasiparticle localization in superconductors with spin-orbit scatteringJun 17 1999We develop a theory of quasiparticle localization in superconductors in situations without spin rotation invariance. We discuss the existence, and properties of superconducting phases with localized/delocalized quasiparticle excitations in such systems ... More
Temporal Order in Dirty Driven Periodic MediaApr 20 1995We consider the non--equilibrium steady states of a driven charge density wave in the presence of impurities and noise. In three dimensions at strong drive, a true dynamical phase transition into a temporally periodic state with quasi--long--range translational ... More
Weak Coupling Phase Diagram of the Two Chain Hubbard ModelMar 09 1995We present a general method for determining the phase diagram of systems of a finite number of one dimensional Hubbard--like systems coupled by single--particle hopping with weak interactions. The technique is illustrated by detailed calculations for ... More
Criticality in the two-dimensional random-bond Ising modelJul 24 1996Nov 13 1996The two-dimensional (2D) random-bond Ising model has a novel multicritical point on the ferromagnetic to paramagnetic phase boundary. This random phase transition is one of the simplest examples of a 2D critical point occurring at both finite temperatures ... More
Entanglement and the Sign Structure of Quantum StatesDec 11 2014Many body quantum eigenstates of generic Hamiltonians at finite energy density typically satisfy "volume law" of entanglement entropy: the von Neumann entanglement entropy and the Renyi entropies for a subregion scale in proportion to its volume. Here ... More
Quantum Disentangled LiquidsJul 08 2013Aug 21 2013We propose and explore a new finite temperature phase of translationally invariant multi-component liquids which we call a "Quantum Disentangled Liquid" (QDL) phase. We contemplate the possibility that in fluids consisting of two (or more) species of ... More
Inelastic neutron scattering signal from deconfined spinons in a fractionalized antiferromagnetApr 17 2002We calculate the contribution of deconfined spinons to inelastic neutron scattering (INS) in the fractionalized antiferromagnet (AF*), introduced elsewhere. We find that the presence of free spin-1/2 charge-less excitations leads to a continuum INS signal ... More
Delocalization Transition via Supersymmetry in one DimensionJun 06 1997We use supersymmetric (SUSY) methods to study the delocalization transition at zero energy in a one-dimensional tight-binding model of spinless fermions with particle-hole symmetric disorder. Like the McCoy-Wu random transverse-field Ising model to which ... More
Correlation Effects in Carbon NanotubesNov 15 1996We consider the effects of Coulomb interactions on single-wall carbon nanotubes using an on-site Hubbard interaction, u. For the (N,N) armchair tubes the low energy theory is shown to be identical to a 2-chain Hubbard model at half-filling, with an effective ... More
Thermal transport in a Luttinger liquidSep 12 1995We study thermal transport in a one-dimensional (1d) interacting electron gas, employing the Luttinger liquid model. Both thermal conductance and thermopower are analyzed for a pure 1d gas and with impurities. The universal ratio of electrical to thermal ... More
Fractionalization in the cuprates: Detecting the topological orderJun 30 2000The precise theoretical characterization of a fractionalized phase in spatial dimensions higher than one is through the concept of ``topological order''. We describe a physical effect that is a robust and direct consequence of this hidden order that should ... More
Shot Noise and the Transmission of Dilute Laughlin QuasiparticlesAug 30 2002We analyze theoretically a three-terminal geometry in a fractional quantum Hall system - studied in a recent experiment - which allows a dilute beam of Laughlin quasiparticles to be prepared and subsequently scattered by a point contact. Employing a chiral ... More
Detecting fractions of electrons in the high-$T_c$ cupratesNov 21 2000We propose several tests of the idea that the electron is fractionalized in the underdoped and undoped cuprates. These include the ac Josephson effect, and tunneling into small superconducting grains in the Coulomb blockade regime. In both cases, we argue ... More
Quasiparticle Localization Transition in Dirty SuperconductorsMar 02 2000May 08 2000In this paper, a delocalization-localization transition within the superconducting state is explored. The symmetries of the Bogoliubov deGennes Hamiltonian endow the two associated superconducting phases - the thermal metal and the thermal insulator-, ... More
Mode-Locking in Quantum-Hall-Effect Point ContactsOct 27 1995Jan 31 1998We study the effect of an ac drive on the current-voltage (I-V) characteristics of a tunnel junction between two fractional Quantum Hall fluids at filling $\nu ^{-1}$ an odd integer. Within the chiral Luttinger liquid model of edge states, the point contact ... More
Interacting topological phases in multiband nanowiresApr 13 2011Dec 19 2011We show that semiconductor nanowires coupled to an s-wave superconductor provide a playground to study effects of interactions between different topological superconducting phases supporting Majorana zero-energy modes. We consider quasi-one dimensional ... More
Graphene integer quantum Hall effect in the ferromagnetic and paramagnetic regimesApr 26 2006Starting from the graphene lattice tight-binding Hamiltonian with an on-site U and long-range Coulomb repulsion, we derive an interacting continuum Dirac theory governing the low-energy behavior of graphene in an applied magnetic field. Initially, we ... More
Fractionalization, topological order, and cuprate superconductivityAug 05 2000This paper is concerned with the idea that the electron is fractionalized in the cuprate high-$T_c$ materials. We show how the notion of topological order may be used to develop a precise theoretical characterization of a fractionalized phase in spatial ... More
Universal Periods in Quantum Hall DropletsMay 10 2007Oct 20 2007Using the hierarchy picture of the fractional quantum Hall effect, we study the the ground state periodicity of a finite size quantum Hall droplet in a quantum Hall fluid of a different filling factor. The droplet edge charge is periodically modulated ... More
A symmetry-respecting topologically-ordered surface phase of 3d electron topological insulatorsJun 14 2013A 3d electron topological insulator (ETI) is a phase of matter protected by particle-number conservation and time-reversal symmetry. It was previously believed that the surface of an ETI must be gapless unless one of these symmetries is broken. A well-known ... More
Bosonic topological insulator in three dimensions and the statistical Witten effectFeb 26 2013It is well-known that one signature of the three-dimensional electron topological insulator is the Witten effect: if the system is coupled to a compact electromagnetic gauge field, a monopole in the bulk acquires a half-odd-integer polarization charge. ... More
Dynamics of a heavy particle in a Luttinger liquidOct 17 1995We study the dynamics of a heavy particle of mass $M$ moving in a one-dimensional repulsively interacting Fermi gas. The Fermi gas is described using the Luttinger model and bosonization. By transforming to a frame co-moving with the heavy particle, we ... More
Low-energy behavior of spin-liquid electron spectral functionsOct 02 2012Dec 22 2012We calculate the electron spectral function for a spin-liquid with a spinon Fermi surface and a Dirac spin-liquid. Calculations are based upon the slave-rotor mean-field theory. We consider the effect of gauge fluctuations using a simple model and find ... More
Non-equilibrium transport through a point contact in the $ν=5/2$ non-Abelian quantum Hall stateSep 08 2008Sep 23 2008We analyze charge-$e/4$ quasiparticle tunneling between the edges of a point contact in a non-Abelian model of the $\nu=5/2$ quantum Hall state. We map this problem to resonant tunneling between attractive Luttinger liquids and use the time-dependent ... More
Erratum: algebraic spin liquid as the mother of many competing ordersSep 19 2007We correct an error in our paper Phys. Rev. B 72, 104404 (2005) [cond-mat/0502215]. We show that a particular fermion bilinear is not related to the other ``competing orders'' of the algebraic spin liquid, and does not possess their slowly decaying correlations. ... More
Theory of the algebraic vortex liquid in an anisotropic spin-1/2 triangular antiferromagnetDec 18 2005We explore spin-1/2 triangular antiferromagnets with both easy-plane and lattice exchange anisotropies by employing a dual vortex mapping followed by a fermionization of the vortices. Over a broad range of exchange anisotropy, this approach leads naturally ... More
Vortices and quasiparticles near the "superconductor-insulator" transition in thin filmsApr 28 2005May 10 2005We study the low temperature behavior of an amorphous superconducting film driven normal by a perpendicular magnetic field (B). For this purpose we introduce a new two-fluid formulation consisting of fermionized field induced vortices and electrically ... More
Quantum entanglement in carbon nanotubesFeb 06 2002With the surge of research in quantum information, the issue of producing entangled states has gained prominence. Here, we show that judiciously bringing together two systems of strongly interacting electrons with vastly differing ground states - the ... More
Dual Vortex Theory of Strongly Interacting Electrons: Non-Fermi Liquid to the (Hard) CoreMar 18 1999Apr 02 1999As discovered in the quantum Hall effect, a very effective way for strongly-repulsive electrons to minimize their potential energy is to aquire non-zero relative angular momentum. We pursue this mechanism for interacting two-dimensional electrons in zero ... More
Quantum-disentangled liquid in the half-filled Hubbard modelNov 07 2016Nov 08 2017We investigate the existence of quantum disentangled liquid (QDL) states in the half-filled Hubbard model on bipartite lattices. In the one dimensional case we employ a combination of integrability and strong coupling expansion methods to argue that there ... More
Dynamical Disentanglement across a Point Contact in a Non-Abelian Quantum Hall StateApr 04 2006May 31 2006We analyze tunneling of non-Abelian quasiparticles between the edges of a quantum Hall droplet at Landau level filling fraction nu=5/2, assuming that the electrons in the first excited Landau level organize themselves in the non-Abelian Moore-Read Pfaffian ... More
Pyrochlore Photons: The U(1) Spin Liquid in a S=1/2 Three-Dimensional Frustrated MagnetMay 17 2003Nov 25 2003We study the S=1/2 Heisenberg antiferromagnet on the pyrochlore lattice in the limit of strong easy-axis exchange anisotropy. We find, using only standard techniques of degenerate perturbation theory, that the model has a U(1) gauge symmetry generated ... More
Nodal Liquid Theory of the Pseudo-Gap Phase of High-Tc SuperconductorsMar 08 1998We introduce and study the nodal liquid, a novel zero-temperature quantum phase obtained by quantum-disordering a d-wave superconductor. It has numerous remarkable properties which lead us to suggest it as an explanation of the pseudo-gap state in underdoped ... More
The N-chain Hubbard Model in Weak CouplingMar 06 1997Jan 31 1998We present a systematic weak-coupling renormalization group (RG) technique for studying a collection of $N$ coupled one-dimensional interacting electron systems, focusing on the example of N-leg Hubbard ladders. For $N=2,3$, we recover previous results, ... More
Chiral Metal as a Ferromagnetic Super Spin ChainAug 09 1996Sep 27 1996The electrons on the surface of a disordered multi-layer integer quantum Hall system constitute an unusual chiral metal with ballistic motion transverse to the field, and diffusive motion parallel to it. We present a non-perturbative analytic treatment ... More
Algebraic spin liquid as the mother of many competing ordersFeb 08 2005Jul 25 2005We study the properties of a class of two-dimensional interacting critical states -- dubbed algebraic spin liquids -- that can arise in two-dimensional quantum magnets. A particular example that we focus on is the staggered flux spin liquid, which plays ... More
Ring exchange, the Bose metal, and bosonization in two dimensionsMar 07 2002Motivated by the high-T_c cuprates, we consider a model of bosonic Cooper pairs moving on a square lattice via ring exchange. We show that this model offers a natural middle ground between a conventional antiferromagnetic Mott insulator and the fully ... More
Mott Transition in An Anyon GasJan 28 1993We introduce and analyze a lattice model of anyons in a periodic potential and an external magnetic field which exhibits a transition from a Mott insulator to a quantum Hall fluid. The transition is characterized by the anyon statistics, $\alpha$, which ... More
Emergent particle-hole symmetry in the half-filled Landau levelMar 17 2016We provide an effective description of a particle-hole symmetric state of electrons in a half-filled Landau level, starting from the traditional approach pioneered by Halperin, Lee and Read. Specifically, we study a system consisting of alternating quasi-one-dimensional ... More
Particle-Hole Symmetry and the Composite Fermi LiquidFeb 18 2015Apr 14 2015The half-filled Landau level is widely believed to be described by the Halperin-Lee-Read theory of the composite Fermi liquid (CFL). In this paper, we develop a theory for the particle-hole conjugate of the CFL, the Anti-CFL, which we argue to be a distinct ... More
Spin Bose-Metal phase in a spin-1/2 model with ring exchange on a two-leg triangular stripFeb 24 2009Recent experiments on triangular lattice organic Mott insulators have found evidence for a 2D spin liquid in proximity to the metal-insulator transition. A Gutzwiller wavefunction study of the triangular lattice Heisenberg model with appropriate four-spin ... More
Partial breakdown of quantum thermalization in a Hubbard-like modelJun 17 2016We study the possible breakdown of quantum thermalization in a model of itinerant electrons on a one-dimensional chain without disorder, with both spin and charge degrees of freedom. The eigenstates of this model exhibit peculiar properties in the entanglement ... More
Algebraic vortex liquid in spin-1/2 triangular antiferromagnets: Scenario for Cs_2CuCl_4Aug 22 2005Sep 28 2005Motivated by inelastic neutron scattering data on Cs_2CuCl_4, we explore spin-1/2 triangular lattice antiferromagnets with both spatial and easy-plane exchange anisotropies, the latter due to an observed Dzyaloshinskii-Moriya interaction. Exploiting a ... More
Quasiparticles in the 111 state and its compressible ancestorsMay 05 2001We investigate the relationship of the spontaneously inter-layer coherent ``111''state of quantum Hall bilayers at total filling factor \nu=1 to ``mutual'' composite fermions, in which vortices in one layer are bound to electrons in the other. Pairing ... More
Quasiparticle transport and localization in high-T_c superconductorsAug 01 1998Oct 08 1998We present a theory of the effects of impurity scattering in d_{x^2-y^2} superconductors and their quantum disordered counterparts, based on a non-linear sigma model formulation. We show the existence, in a quasi-two-dimensional system, of a novel spin-metal ... More
Exact SO(8) Symmetry in the Weakly-Interacting Two-Leg LadderJan 28 1998A perturbative renormalization group analysis of interacting electrons on a two-leg ladder reveals that at half-filling any weakly repulsive system scales onto an exactly soluble Gross-Neveu model with a hidden SO(8) symmetry. The half-filled ground state ... More
Partial breakdown of quantum thermalization in a Hubbard-like modelJun 17 2016Feb 09 2017We study the possible breakdown of quantum thermalization in a model of itinerant electrons on a one-dimensional chain without disorder, with both spin and charge degrees of freedom. The eigenstates of this model exhibit peculiar properties in the entanglement ... More
The spin quantum Hall effect in unconventional superconductorsFeb 03 1999We study the properties of the "spin quantum Hall fluid" - a novel spin phase with quantized spin Hall conductance that is potentially realizable in superconducting systems with unconventional pairing symmetry. A simple realization is provided by a $d_{x^2-y^2} ... More
Transport of Surface States in the Bulk Quantum Hall EffectAug 05 1997The two-dimensional surface of a coupled multilayer integer quantum Hall system consists of an anisotropic chiral metal. This unusual metal is characterized by ballistic motion transverse and diffusive motion parallel (\hat{z}) to the magnetic field. ... More
Atypical energy eigenstates in the Hubbard chain and quantum disentangled liquidsNov 07 2017We investigate the implications of integrability for the existence of quantum disentangled liquid (QDL) states in the half-filled one-dimensional Hubbard model. We argue that there exist finite energy-density eigenstates that exhibit QDL behaviour in ... More
Quantum-disentangled liquid in the half-filled Hubbard modelNov 07 2016We investigate the existence of a quantum disentangled liquid (QDL) phase of matter in the half-filled Hubbard model on bipartite lattices. In the one dimensional case we demonstrate that there are indeed finite energy-density eigenstates that exhibit ... More
Boundary Conformal Field Theory and Tunneling of Edge Quasiparticles in non-Abelian Topological StatesFeb 05 2009We explain how (perturbed) boundary conformal field theory allows us to understand the tunneling of edge quasiparticles in non-Abelian topological states. The coupling between a bulk non-Abelian quasiparticle and the edge is due to resonant tunneling ... More
Charge accumulation on a Luttinger liquidDec 08 2003The average charge Q on a quantum wire, modeled as a single-channel Luttinger liquid, connected to metallic leads and coupled to a gate is studied theoretically. We find that the behavior of the charge as the gate voltage V_G varies depends strongly on ... More
The Electron Spectral Function in Two-Dimensional Fractionalized PhasesJan 17 2001We study the electron spectral function of various zero-temperature spin-charge separated phases in two dimensions. In these phases, the electron is not a fundamental excitation of the system, but rather ``decays'' into a spin-1/2 chargeless fermion (the ... More
Topological Entanglement Entropy from the Holographic Partition FunctionSep 05 2006We study the entropy of chiral 2+1-dimensional topological phases, where there are both gapped bulk excitations and gapless edge modes. We show how the entanglement entropy of both types of excitations can be encoded in a single partition function. This ... More
Edge states and tunneling of non-Abelian quasiparticles in the nu=5/2 quantum Hall state and p+ip superconductorsJul 18 2006We study quasiparticle tunneling between the edges of a non-Abelian topological state. The simplest examples are a p+ip superconductor and the Moore-Read Pfaffian non-Abelian fractional quantum Hall state; the latter state may have been observed at Landau-level ... More
Measuring Fractional Charge in Carbon NanotubesAug 11 2000The Luttinger model of the one-dimensional Fermi gas is the cornerstone of modern understanding of interacting electrons in one dimension. In fact, the enormous class of systems whose universal behavior is adiabatically connected to it are now deemed ... More
Quantum Confinement Transition in a d-wave SuperconductorJun 30 2000We study the nature of the zero-temperature phase transition between a d-wave superconductor and a Mott insulator in two dimensions. In this ``quantum confinement transition'', spin and charge are confined to form the electron in the Mott insulator. Within ... More
Superconducting ``metals'' and ``insulators''Jun 16 1999We propose a characterization of zero temperature phases in disordered superconductors on the basis of the nature of quasiparticle transport. In three dimensional systems, there are two distinct phases in close analogy to the distinction between normal ... More
Exotic quantum phases and phase transitions in correlated matterNov 21 2005We present a pedagogical overview of recent theoretical work on unconventional quantum phases and quantum phase transitions in condensed matter systems. Strong correlations between electrons can lead to a breakdown of two traditional paradigms of solid ... More
Spin, Bose, and Non-Fermi Liquid Metals in Two Dimensions: Accessing via Multi-Leg LaddersDec 16 2008Characterizing and accessing quantum phases of itinerant bosons or fermions in two dimensions (2D) that exhibit singular structure along surfaces in momentum space but have no quasi-particle description remains as a central challenge in the field of strongly ... More
Andreev current in finite sized carbon nanotubesJun 13 2002We investigate the effect of interactions on Andreev current at a normal-superconducting junction when the normal phase is a Luttinger liquid with repulsive interactions. In particular, we study the system of a finite sized carbon nanotube placed between ... More
Critical Dynamics of Superconductors in the Charged RegimeJun 30 2003Feb 27 2004We investigate the finite temperature critical dynamics of three-dimensional superconductors in the charged regime, described by a transverse gauge field coupling to the superconducting order parameter. Assuming relaxational dynamics for both the order ... More
Quantum Zeno Effect and the Many-body Entanglement TransitionAug 18 2018Nov 19 2018We introduce and explore a one-dimensional "hybrid" quantum circuit model consisting of both unitary gates and projective measurements. While the unitary gates are drawn from a random distribution and act uniformly in the circuit, the measurements are ... More
Measurement-driven entanglement transition in hybrid quantum circuitsJan 23 2019In this paper we continue to explore "hybrid" quantum circuit models in one-dimension with both unitary and measurement gates, focussing on the entanglement properties of wavefunction trajectories at long times, in the steady state. We simulate a large ... More
Wavefunction positivization via automatic differentiationJun 11 2019We introduce a procedure to systematically search for a local unitary transformation that maps a wavefunction with a non-trivial sign structure into a positive-real form. The transformation is parametrized as a quantum circuit compiled into a set of one ... More
Spin Bose-Metal and Valence Bond Solid phases in a spin-1/2 model with ring exchanges on a four-leg triangular ladderSep 06 2010May 19 2011We study a spin-1/2 system with Heisenberg plus ring exchanges on a four-leg triangular ladder using the density matrix renormalization group and Gutzwiller variational wave functions. Near an isotropic lattice regime, for moderate to large ring exchanges ... More
Atomic quantum simulator for lattice gauge theories and ring exchange modelsMar 10 2005Mar 22 2005We present the design of a ring exchange interaction in cold atomic gases subjected to an optical lattice using well understood tools for manipulating and controlling such gases. The strength of this interaction can be tuned independently and describes ... More
Interaction Effects in Topological Superconducting Wires Supporting Majorana FermionsApr 28 2011Among the broad spectrum of systems predicted to exhibit topological superconductivity and Majorana fermions, one-dimensional wires with strong spin-orbit coupling provide one of the most promising experimental candidates. Here we investigate the fate ... More
Resonant Multi-Lead Point-Contact TunnelingOct 29 1997We analyze a model of resonant point-contact tunneling between multiple Luttinger liquid leads. The model is a variant of the multi-channel Kondo model and can be related to the quantum Brownian motion of a particle on lattices with $\pi$-flux through ... More
Monopoles in CP(N-1) model via the state-operator correspondenceSep 17 2008One of the earliest proposed phase transitions beyond the Landau-Ginzburg-Wilson paradigm is the quantum critical point separating an antiferromagnet and a valence-bond-solid on a square lattice. The low energy description of this transition is believed ... More
On the stability of U(1) spin liquids in two dimensionsApr 30 2004Oct 14 2004We establish that spin liquids described in terms of gapless fermionic (Dirac) spinons and gapless U(1) gauge fluctuations can be stable in two dimensions, at least when the physical SU(2) spin symmetry is generalized to SU(N). Equivalently, we show that ... More
Majorana Zero Modes in 1D Quantum Wires Without Long-Ranged Superconducting OrderJun 14 2011Jul 06 2011We show that long-ranged superconducting order is not necessary to guarantee the existence of Majorana fermion zero modes at the ends of a quantum wire. We formulate a concrete model which applies, for instance, to a semiconducting quantum wire with strong ... More