334 research outputs found
Effect of nonadiabatic switching of dynamic perturbations in 1d Fermi systems
We study a two-dimensional fermionic QFT used to model 1D strongly correlated
electrons in the presence of a time-dependent impurity that drives the system
out of equilibrium. In contrast to previous investigations, we consider a
dynamic barrier switched on at a finite time. We compute the total energy
density (TED) of the system and establish two well defined regimes in terms of
the relationship between the frequency of the time-dependent perturbation
and the electron energy . Finally, we derive a relaxation time
such that for times shorter than the finite-time switching
process is relevant.Comment: 9 pages, 4 figures. Changed title. Added comments on backscattering.
Added result for electrical current. Version accepted in PR
Fermi Edge Singularities and Backscattering in a Weakly Interacting 1D Electron Gas
The photon-absorption edge in a weakly interacting one-dimensional electron
gas is studied, treating backscattering of conduction electrons from the core
hole exactly. Close to threshold, there is a power-law singularity in the
absorption, , with where is the forward scattering
phase shift of the core hole. In contrast to previous theories, is
finite (and universal) in the limit of weak core hole potential. In the case of
weak backscattering , the exponent in the power-law dependence of
absorption on energy crosses over to a value above an energy scale , where is a dimensionless measure of the
electron-electron interactions.Comment: 8 pages + 1 postscript figure, preprint TPI-MINN-93/40-
Solitonic excitations in the Haldane phase of a S=1 chain
We study low-lying excitations in the 1D antiferromagnetic
valence-bond-solid (VBS) model. In a numerical calculation on finite systems
the lowest excitations are found to form a discrete triplet branch, separated
from the higher-lying continuum. The dispersion of these triplet excitations
can be satisfactorily reproduced by assuming approximate wave functions. These
wave functions are shown to correspond to moving hidden domain walls, i.e. to
one-soliton excitations.Comment: RevTex 3.0, 24 pages, 2 figures on request by fax or mai
Interacting Electrons on a Square Fermi Surface
Electronic states near a square Fermi surface are mapped onto quantum chains.
Using boson-fermion duality on the chains, the bosonic part of the interaction
is isolated and diagonalized. These interactions destroy Fermi liquid behavior.
Non-boson interactions are also generated by this mapping, and give rise to a
new perturbation theory about the boson problem. A case with strong repulsions
between parallel faces is studied and solved. There is spin-charge separation
and the square Fermi surface remains square under doping. At half-filling,
there is a charge gap and insulating behavior together with gapless spin
excitations. This mapping appears to be a general tool for understanding the
properties of interacting electrons on a square Fermi surface.Comment: 25 pages, Nordita preprint 94/22
Spin Gap and Superconductivity in Weakly Coupled Ladders: Interladder One-particle vs. Two-particle Crossover
Effects of the interladder one-particle hopping, , on the
low-energy asymptotics of a weakly coupled Hubbard ladder system have been
studied, based on the perturbative renormalization-group approach. We found
that for finite intraladder Hubbard repulsion, , there exists a crossover
value of the interladder one-particle hopping, . For
, the spin gap metal (SGM) phase of the isolated
ladder transits at a finite transition temperature, , to the d-wave
superconducting (SCd) phase via a two-particle crossover. In the temperature
region, , interladder coherent Josephson tunneling of the Cooper pairs
occurs, while the interladder coherent one-particle process is strongly
suppressed. For , around a crossover temperature,
, the system crosses over to the two-dimensional (2D) phase via a
one-particle crossover. In the temperature region, , the
interladdercoherent band motion occurs.Comment: 4 pages, 5 eps figures, uses jpsj.st
Bosonization on the lattice: the emergence of the higher harmonics
A general and transparent procedure to bosonize fermions placed on a lattice
is presented. Harmonics higher than are shown to appear in the
one-paticle Green function, due to the compact character of real electron
bands. Quantitative estimations of the role of these higher harmonics are made
possible by the bosonization technique presented here.Comment: Pages: 15 (REVTEX 3.0) plus 4 postscript figures appended at the end
of the tex
Coulomb drag between one-dimensional conductors
We have analyzed Coulomb drag between currents of interacting electrons in
two parallel one-dimensional conductors of finite length attached to
external reservoirs. For strong coupling, the relative fluctuations of electron
density in the conductors acquire energy gap . At energies larger than
, where
is the impurity scattering rate, and for , where is the
fluctuation velocity, the gap leads to an ``ideal'' drag with almost equal
currents in the conductors. At low energies the drag is suppressed by coherent
instanton tunneling, and the zero-temperature transconductance vanishes,
indicating the Fermi liquid behavior.Comment: 5 twocolumn pages in RevTex, added 1 eps-Figure and calculation of
trans-resistanc
NON-METALLIC REINFORCEMENTS WITH DIFFERENT MODULI OF ELASTICITY AND SURFACES FOR CONCRETE STRUCTURES
Power laws in a 2-leg ladder of interacting spinless fermions
We use the Density-Matrix Renormalization Group to study the single-particle
and two-particle correlation functions of spinless fermions in the ground state
of a quarter-filled ladder. This ladder consists of two chains having an
in-chain extended Coulomb interaction reaching to third neighbor and coupled by
inter-chain hopping. Within our short numerical coherence lengths, typically
reaching ten to twenty sites, we find a strong renormalization of the
interchain hopping and the existence of a dimensional crossover at smaller
interactions. We also find power exponents for single-particle hopping and
interchain polarization consistent with the single chain. The total charge
correlation function has a larger power exponent and shows signs of a crossover
from incoherent fermion hopping to coherent particle-hole pair motion between
chains. There are no significant excitation energies.Comment: RevTex 4 file, 10 pages, 10 eps figure
Nonequilibrium Electron Distribution in Presence of Kondo Impurities
We study the energy relaxation of quasiparticles in voltage biased mesoscopic
wires in presence of magnetic impurities. The renormalization of the exchange
interaction of Kondo impurities coupled to conduction electrons is extended to
the case of a nonequilibrium electron distribution, which is determined
self-consistently from a Boltzmann equation with a collision term due to Kondo
impurity mediated electron-electron scattering. The approach leads to
predictions in quantitative agreement with recent experiments by Pothier et al.
[Phys. Rev. Lett. 79, 3490 (1997)].Comment: 4 pages, 3 figure
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