229 research outputs found
Exotic resonant level models in non-Abelian quantum Hall states coupled to quantum dots
In this paper we study the coupling between a quantum dot and the edge of a
non-Abelian fractional quantum Hall state. We assume the dot is small enough
that its level spacing is large compared to both the temperature and the
coupling to the spatially proximate bulk non-Abelian fractional quantum Hall
state. We focus on the physics of level degeneracy with electron number on the
dot. The physics of such a resonant level is governed by a -channel Kondo
model when the quantum Hall state is a Read-Rezayi state at filling fraction
or its particle-hole conjugate at . The
-channel Kondo model is channel symmetric even without fine tuning any
couplings in the former state; in the latter, it is generically channel
asymmetric. The two limits exhibit non-Fermi liquid and Fermi liquid
properties, respectively, and therefore may be distinguished. By exploiting the
mapping between the resonant level model and the multichannel Kondo model, we
discuss the thermodynamic and transport properties of the system. In the
special case of , our results provide a novel venue to distinguish between
the Pfaffian and anti-Pfaffian states at filling fraction . We present
numerical estimates for realizing this scenario in experiment.Comment: 18 pages, 2 figures. Clarified final discussio
Zn-induced spin dynamics in overdoped LaSrCuZnO
Spin fluctuations and the local spin susceptibility in isovalently
Zn-substituted LaSrCuZnO (,
) are measured via inelastic neutron scattering techniques. As
Zn is substituted onto the Cu-sites, an anomalous enhancement of
the local spin susceptibility appears due to the
emergence of a commensurate antiferromagnetic excitation centered at wave
vector \textbf{Q} that coexists with the known incommensurate
SDW excitations at \textbf{Q}.
Our results support a picture of Zn-induced antiferromagnetic (AF) fluctuations
appearing through a local staggered polarization of Cu-spins, and the
simultaneous suppression of T as AF fluctuations are slowed in proximity to
Zn-impurities suggests the continued importance of high energy AF fluctuations
at the far overdoped edge of superconductivity in the cuprates.Comment: 10 pages, 8 figure
Utilization of cardiovascular magnetic resonance (CMR) imaging for resumption of athletic activities following COVID-19 infection: An expert consensus document on behalf of the American Heart Association Council on Cardiovascular Radiology and Intervention (CVRI) Leadership and endorsed by the Society for Cardiovascular Magnetic Resonance (SCMR)
The global pandemic of coronavirus disease 2019 (COVID-19) caused by infection with severe acute respiratory suyndrome coronavirus 2 (SARS-CoV-2) is now entering its 4th year with little evidence of abatement. As of December 2022, the World Health Organization Coronavirus (COVID-19) Dashboard reported 643 million cumulative confirmed cases of COVID-19 worldwide and 98 million in the United States alone as the country with the highest number of cases. While pneumonia with lung injury has been the manifestation of COVID-19 principally responsible for morbidity and mortality, myocardial inflammation and systolic dysfunction though uncommon are well-recognized features that also associate with adverse prognosis. Given the broad swath of the population infected with COVID-19, the large number of affected professional, collegiate, and amateur athletes raises concern regarding the safe resumption of athletic activity (return to play, RTP) following resolution of infection. A variety of different testing combinations that leverage the electrocardiogram, echocardiography, circulating cardiac biomarkers, and cardiovascular magnetic resonance (CMR) imaging have been proposed and implemented to mitigate risk. CMR in particular affords high sensitivity for myocarditis but has been employed and interpreted non-uniformly in the context of COVID-19 thereby raising uncertainty as to the generalizability and clinical relevance of findings with respect to RTP. This consensus document synthesizes available evidence to contextualize the appropriate utilization of CMR in the RTP assessment of athletes with prior COVID-19 infection to facilitate informed, evidence-based decisions, while identifying knowledge gaps that merit further investigation
Confinement of Slave-Particles in U(1) Gauge Theories of Strongly-Interacting Electrons
We show that slave particles are always confined in U(1) gauge theories of
interacting electron systems. Consequently, the low-lying degrees of freedom
are different from the slave particles. This is done by constructing a dual
formulation of the slave-particle representation in which the no-double
occupany constraint becomes linear and, hence, soluble. Spin-charge separation,
if it occurs, is due to the existence of solitons with fractional quantum
numbers
Quasiparticle scattering and local density of states in the d-density wave phase
We study the effects of single-impurity scattering on the local density of
states in the high- cuprates. We compare the quasiparticle interference
patterns in three different ordered states: d-wave superconductor (DSC),
d-density wave (DDW), and coexisting DSC and DDW (DSC-DDW). In the coexisting
state, at energies below the DSC gap, the patterns are almost identical to
those in the pure DSC state with the same DSC gap. However, they are
significantly different for energies greater than or equal to the DSC gap. This
transition at an energy around the DSC gap can be used to test the nature of
the superconducting state of the underdoped cuprates by scanning tunneling
microscopy. Furthermore, we note that in the DDW state the effect of the
coherence factors is stronger than in the DSC state. The new features arising
due to DDW ordering are discussed.Comment: 6 page, 5 figures (Higher resolution figures are available by
request
Competing Orders in Coupled Luttinger Liquids
We consider the problem of two coupled Luttinger liquids both at half filling
and at low doping levels, to investigate the problem of competing orders in
quasi-one-dimensional strongly correlated systems. We use bosonization and
renormalization group equations to investigate the phase diagrams, to determine
the allowed phases and to establish approximate boundaries among them. Because
of the chiral translation and reflection symmetry in the charge mode away from
half filling, orders of charge density wave (CDW) and spin-Peierls (SP)
diagonal current (DC) and -density wave (DDW) form two doublets and thus can
be at most quasi-long range ordered. At half-filling, umklapp terms break this
symmetry down to a discrete group and thus Ising-type ordered phases appear as
a result of spontaneous breaking of the residual symmetries. Quantum disordered
Haldane phases are also found, with finite amplitudes of pairing orders and
triplet counterparts of CDW, SP, DC and DDW. Relations with recent numerical
results and implications to similar problems in two dimensions are discussed.Comment: 16 pages, 5 figures, 4 tables. Revised manuscript; a misprint in Eq.
B3 has been corrected. The paper is already in print in PR
Non-Abelian Anyons and Topological Quantum Computation
Topological quantum computation has recently emerged as one of the most
exciting approaches to constructing a fault-tolerant quantum computer. The
proposal relies on the existence of topological states of matter whose
quasiparticle excitations are neither bosons nor fermions, but are particles
known as {\it Non-Abelian anyons}, meaning that they obey {\it non-Abelian
braiding statistics}. Quantum information is stored in states with multiple
quasiparticles, which have a topological degeneracy. The unitary gate
operations which are necessary for quantum computation are carried out by
braiding quasiparticles, and then measuring the multi-quasiparticle states. The
fault-tolerance of a topological quantum computer arises from the non-local
encoding of the states of the quasiparticles, which makes them immune to errors
caused by local perturbations. To date, the only such topological states
thought to have been found in nature are fractional quantum Hall states, most
prominently the \nu=5/2 state, although several other prospective candidates
have been proposed in systems as disparate as ultra-cold atoms in optical
lattices and thin film superconductors. In this review article, we describe
current research in this field, focusing on the general theoretical concepts of
non-Abelian statistics as it relates to topological quantum computation, on
understanding non-Abelian quantum Hall states, on proposed experiments to
detect non-Abelian anyons, and on proposed architectures for a topological
quantum computer. We address both the mathematical underpinnings of topological
quantum computation and the physics of the subject using the \nu=5/2 fractional
quantum Hall state as the archetype of a non-Abelian topological state enabling
fault-tolerant quantum computation.Comment: Final Accepted form for RM
Fractionalization patterns in strongly correlated electron systems: Spin-charge separation and beyond
We discuss possible patterns of electron fractionalization in strongly
interacting electron systems. A popular possibility is one in which the charge
of the electron has been liberated from its Fermi statistics. Such a
fractionalized phase contains in it the seed of superconductivity. Another
possibility occurs when the spin of the electron, rather than its charge, is
liberated from its Fermi statistics. Such a phase contains in it the seed of
magnetism, rather than superconductivity. We consider models in which both of
these phases occur and study possible phase transitions between them. We
describe other fractionalized phases, distinct from these, in which fractions
of the electron themselves fractionalize, and discuss the topological
characterization of such phases. These ideas are illustrated with specific
models of p-wave superconductors, Kondo lattices, and coexistence between
d-wave superconductivity and antiferromagnetism.Comment: 28 pages, 11 fig
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