1,911 research outputs found
Haldane Sashes in Quantum Hall Spectra
We show that the low-temperature sash features in the lowest Landau-level
(LLL) tunneling density-of-states (TDOS) recently discovered by Dial and
Ashoori are intimately related to the discrete Haldane-pseudopotential
interaction energy scales that govern fractional quantum Hall physics. Our
analysis is based on expressions for the tunneling density-of-states which
become exact at filling factors close to and , where the sash
structure is most prominent. We comment on other aspects of LLL correlation
physics that can be revealed by accurate temperature-dependent tunneling data.Comment: Added referenc
Spin-Seebeck effect in a strongly interacting Fermi gas
We study the spin-Seebeck effect in a strongly interacting, two-component
Fermi gas and propose an experiment to measure this effect by relatively
displacing spin up and spin down atomic clouds in a trap using spin-dependent
temperature gradients. We compute the spin-Seebeck coefficient and related
spin-heat transport coefficients as functions of temperature and interaction
strength. We find that when the inter-spin scattering length becomes larger
than the Fermi wavelength, the spin-Seebeck coefficient changes sign as a
function of temperature, and hence so does the direction of the
spin-separation. We compute this zero-crossing temperature as a function of
interaction strength and in particular in the unitary limit for the inter-spin
scattering
Luttinger Liquid at the Edge of a Graphene Vacuum
We demonstrate that an undoped two-dimensional carbon plane (graphene) whose
bulk is in the integer quantum Hall regime supports a non-chiral Luttinger
liquid at an armchair edge. This behavior arises due to the unusual dispersion
of the non-interacting edges states, causing a crossing of bands with different
valley and spin indices at the edge. We demonstrate that this stabilizes a
domain wall structure with a spontaneously ordered phase degree of freedom.
This coherent domain wall supports gapless charged excitations, and has a power
law tunneling with a non-integral exponent. In proximity to a bulk lead,
the edge may undergo a quantum phase transition between the Luttinger liquid
phase and a metallic state when the edge confinement is sufficiently strong
relative to the interaction energy scale.Comment: 4 pages, 3 figure
Heat pumping with optically driven excitons
We present a theoretical study showing that an optically driven excitonic
two-level system in a solid state environment acts as a heat pump by means of
repeated phonon emission or absorption events. We derive a master equation for
the combined phonon bath and two-level system dynamics and analyze the
direction and rate of energy transfer as a function of the externally
accessible driving parameters. We discover that if the driving laser is detuned
from the exciton transition, cooling the phonon environment becomes possible
Quantum heat transfer: A Born Oppenheimer method
We develop a Born-Oppenheimer type formalism for the description of quantum
thermal transport along hybrid nanoscale objects. Our formalism is suitable for
treating heat transfer in the off-resonant regime, where e.g., the relevant
vibrational modes of the interlocated molecule are high relative to typical
bath frequencies, and at low temperatures when tunneling effects dominate. A
general expression for the thermal energy current is accomplished, in the form
of a generalized Landauer formula. In the harmonic limit this expression
reduces to the standard Landauer result for heat transfer, while in the
presence of nonlinearities multiphonon tunneling effects are realized
Interaction-Enhanced Coherence Between Two-Dimensional Dirac Layers
We estimate the strength of interaction-enhanced coherence between two
graphene or topological insulator surface-state layers by solving
imaginary-axis gap equations in the random phase approximation. Using a
self-consistent treatment of dynamic screening of Coulomb interactions in the
gapped phase, we show that the excitonic gap can reach values on the order of
the Fermi energy at strong interactions. The gap is discontinuous as a function
of interlayer separation and effective fine structure constant, revealing a
first order phase transition between effectively incoherent and interlayer
coherent phases. To achieve the regime of strong coherence the interlayer
separation must be smaller than the Fermi wavelength, and the extrinsic
screening of the medium embedding the Dirac layers must be negligible. In the
case of a graphene double-layer we comment on the supportive role of the remote
-bands neglected in the two-band Dirac model.Comment: 14 pages, 9 figure
Using Josephson junctions to determine the pairing state of superconductors without crystal inversion symmetry
Theoretical studies of a planar tunnel junction between two superconductors
with antisymmetric spin-orbit coupling are presented. The half-space Green's
function for such a superconductor is determined. This is then used to derive
expressions for the dissipative current and the Josephson current of the
junction. Numerical results are presented in the case of the Rashba spin-orbit
coupling, relevant to the much studied compound CePtSi. Current-voltage
diagrams, differential conductance and the critical Josephson current are
presented for different crystallographic orientations and different weights of
singlet and triplet components of the pairing state. The main conclusion is
that Josephson junctions with different crystallographic orientations may
provide a direct connection between unconventional pairing in superconductors
of this kind and the absence of inversion symmetry in the crystal.Comment: 16 pages, 10 figure
Edge Magnetoplasmons in Quantum Hall Line Junction Systems
A quantum Hall line junction system consists of a one-dimensional Luttinger
liquid (LL) and two chiral channels that allow density waves incident upon and
reflected by the LL to be measured separately. We demonstrate that interactions
in a quantum Hall line junction system can be probed by studying edge
magnetoplasmon absorption spectra and their polarization dependences. Strong
interactions in the junction lead to collective modes that are isolated in
either Luttinger liquid or contact subsystems.Comment: 4 pages, 3 figures, submitted to Phys. Rev. B Rapid Communicatio
Optical conductivity for a dimer in the Dynamic Hubbard model
The Dynamic Hubbard Model represents the physics of a multi-band Hubbard
model by using a pseudo-spin degree of freedom to dynamically modify the
on-site Coulomb interaction. Here we use a dimer system to obtain analytical
results for this model. The spectral function and the optical conductivity are
calculated analytically for any number of electrons, and the distribution of
optical spectral weight is analyzed in great detail. The impact of polaron-like
effects due to overlaps between pseudo-spin states on the optical spectral
weight distribution is derived analytically. Our conclusions support results
obtained previously with different models and techniques: holes are less mobile
than electrons.Comment: 11 pages, 4 figure
- …