71,967 research outputs found
Study of the triangular lattice tV model near x=1/3
We study extended Hubbard model on a triangular lattice near doping ,
which may be relevant for the recently discovered superconductor NaCoOHO. By generalizing this model to fermionic species, we
formulate a meanfield description in the limit of large . In meanfield, we
find two possible phases: a renormalized Fermi liquid and a \rt3rt3 charge
density wave state. The transition between the two phases is driven by
increasing the nearest neighbor repulsion and is found to be first order for
doping , but occurs close to the point of the local instability of the
uniform liquid. We also study fluctuations about the uniform meanfield state in
a systematic 1/N expansion, focusing on the residual interaction of
quasiparticles and possible superconducting instabilities due to this
interaction. Upon moving towards the CDW instability, the increasing charge
fluctuations favor a particular -wave triplet state. (This state was
recently discussed by Tanakaet al, cond-mat/0311266). We also report a direct
Gutzwiller wavefunction study of the spin-1/2 model.Comment: 9 pages, 5 figure
Scalar Aharonov-Bohm effect with longitudinally polarized neutrons
In the scalar Aharonov-Bohm effect, a charged particle (electron) interacts with the scalar electrostatic potential U in the field-free (i.e., force-free) region inside an electrostatic cylinder (Faraday cage). Using a perfect single-crystal neutron interferometer we have performed a “dual” scalar Aharonov-Bohm experiment by subjecting polarized thermal neutrons to a pulsed magnetic field. The pulsed magnetic field was spatially uniform, precluding any force on the neutrons. Aligning the direction of the pulsed magnetic field to the neutron magnetic moment also rules out any classical torque acting to change the neutron polarization. The observed phase shift is purely quantum mechanical in origin. A detailed description of the experiment, performed at the University of Missouri Research Reactor, and its interpretation is given in this paper
Influences of an impurity on the transport properties of one-dimensional antisymmetric spin filter
The influences of an impurity on the spin and the charge transport of
one-dimensional antisymmetric spin filter are investigated using bosonization
and Keldysh formulation and the results are highlighted against those of
spinful Luttinger liquids. Due to the dependence of the electron spin
orientation on wave number the spin transport is not affected by the impurity,
while the charge transport is essentially identical with that of spinless
one-dimensional Luttinger liquid.Comment: 7 pages, 2 figures. To appear in Physical Review
Phase diagram of the three band half-filled Cu-O two-leg ladder
We determine the phase diagram of the half-filled two-leg ladder both at weak
and strong coupling, taking into account the Cu d_{x^2-y^2} and the O p_x and
p_y orbitals. At weak coupling, renormalization group flows are interpreted
with the use of bosonization. Two different models with and without outer
oxygen orbitals are examined. For physical parameters, and in the absence of
the outer oxygen orbitals, the D-Mott phase arises; a dimerized phase appears
when the outer oxygen atoms are included. We show that the circulating current
phase that preserves translational symmetry does not appear at weak coupling.
In the opposite strong-coupling atomic limit the model is purely electrostatic
and the ground states may be found by simple energy minimization. The phase
diagram so obtained is compared to the weak-coupling one.Comment: 10 pages, 5 figures, Version accepted for publication in PR
Collective excitation of quantum wires and effect of spin-orbit coupling in the presence of a magnetic field along the wire
The band structure of a quantum wire with the Rashba spin-orbit coupling
develops a pseudogap in the presence of a magnetic field along the wire. In
such a system spin mixing at the Fermi wavevectors and can be
different. We have investigated theoretically the collective mode of this
system, and found that the velocity of this collective excitation depends
sensitively on the strength of the Rashba spin-orbit interaction and magnetic
field. Our result suggests that the strength of the spin-orbit interaction can
be determined from the measurement of the velocity.Comment: RevTeX 4 file, 4pages, 6 eps figures. To appear in Physical Review
Josephson current in strongly correlated double quantum dots
We study the transport properties of a serial double quantum dot (DQD)
coupled to two superconducting leads, focusing on the Josephson current through
the DQD and the associated 0- transitions which result from the subtle
interplay between the superconductivity, the Kondo physics, and the inter-dot
superexchange interaction. We examine the competition between the
superconductivity and the Kondo physics by tuning the relative strength
of the superconducting gap and the Kondo temperature
, for different strengths of the superexchange coupling determined by the
interdot tunneling relative to the dot level broadening . We find
strong renormalization of , a significant role of the superexchange coupling
, and a rich phase diagram of the 0 and -junction regimes. In
particular, when both the superconductivity and the exchange interaction are in
close competion with the Kondo physics (), there appears
an island of -phase at large values of the superconducting phase
difference.Comment: 4 pages, 4 figure
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