9,308 research outputs found
Kondo Breakdown as a Selective Mott Transition in the Anderson Lattice
We show within the slave boson technique, that the Anderson lattice model
exhibits a Kondo breakdown quantum critical point (KB-QCP) where the
hybridization goes to zero at zero temper- ature. At this fixed point, the
f-electrons experience as well a selective Mott transition separating a
local-moment phase from a Kondo-screened phase. The presence of a multi-scale
QCP in the An- derson lattice in the absence of magnetism is discussed in the
context of heavy fermion compounds. This study is the first evidence for a
selective Mott transition in the Anderson lattice.Comment: 4 pages, 2 figures, version with new figures and typos correcte
Attractive Fermi gases with unequal spin populations in highly elongated traps
We investigate two-component attractive Fermi gases with imbalanced spin
populations in trapped one dimensional configurations. The ground state
properties are determined within local density approximation, starting from the
exact Bethe-ansatz equations for the homogeneous case. We predict that the
atoms are distributed according to a two-shell structure: a partially polarized
phase in the center of the trap and either a fully paired or a fully polarized
phase in the wings. The partially polarized core is expected to be a superfluid
of the FFLO type. The size of the cloud as well as the critical spin
polarization needed to suppress the fully paired shell, are calculated as a
function of the coupling strength.Comment: Final accepted versio
Phase diagram of asymmetric Fermi gas across Feshbach resonance
We study the phase diagram of the dilute two-component Fermi gas at zero
temperature as a function of the polarization and coupling strength. We map out
the detailed phase separations between superfluid and normal states near the
Feshbach resonance. We show that there are three different coexistence of
superfluid and normal phases corresponding to phase separated states between:
(I) the partially polarized superfluid and the fully polarized normal phases,
(II) the unpolarized superfluid and the fully polarized normal phases and (III)
the unpolarized superfluid and the partially polarized normal phases from
strong-coupling BEC side to weak-coupling BCS side. For pairing between two
species, we found this phase separation regime gets wider and moves toward the
BEC side for the majority species are heavier but shifts to BCS side and
becomes narrow if they are lighter.Comment: 4 pages, 3 figures. Submitted to LT25 on June 200
Pairing of a trapped resonantly-interacting fermion mixture with unequal spin populations
We consider the phase separation of a trapped atomic mixture of fermions with
unequal spin populations near a Feshbach resonance. In particular, we determine
the density profile of the two spin states and compare with the recent
experiments of Partridge et al. (cond-mat/0511752). Overall we find quite good
agreement. We identify the remaining discrepancies and pose them as open
problems.Comment: 4 figures, 4+ pages, revtex
The low temperature Fulde-Ferrell-Larkin-Ovchinnikov phases in 3 dimensions
We consider the nature of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phases
in three dimensions at low temperature. We introduce a new method to handle the
quasiclassical equations for superconductors with space dependent order
parameter, which makes use of a Fourier expansion. This allows us to show that,
at T=0, an order parameter given by the linear combination of three cosines
oscillating in orthogonal directions is preferred over the standard single
cosine solution. The transition from the normal state to this phase is first
order, and quite generally the transition below the tricritical point to the
FFLO phases is always first order.Comment: 4 pages, revtex, 1 figur
Finite-momentum Bose-Einstein condensates in shaken 2D square optical lattices
We consider ultracold bosons in a 2D square optical lattice described by the
Bose-Hubbard model. In addition, an external time-dependent sinusoidal force is
applied to the system, which shakes the lattice along one of the diagonals. The
effect of the shaking is to renormalize the nearest-neighbor hopping
coefficients, which can be arbitrarily reduced, can vanish, or can even change
sign, depending on the shaking parameter. It is therefore necessary to account
for higher-order hopping terms, which are renormalized differently by the
shaking, and introduce anisotropy into the problem. We show that the
competition between these different hopping terms leads to finite-momentum
condensates, with a momentum that may be tuned via the strength of the shaking.
We calculate the boundaries between the Mott-insulator and the different
superfluid phases, and present the time-of-flight images expected to be
observed experimentally. Our results open up new possibilities for the
realization of bosonic analogs of the FFLO phase describing inhomogeneous
superconductivity.Comment: 7 pages, 7 figure
The Amplitude of Non-Equilibrium Quantum Interference in Metallic Mesoscopic Systems
We study the influence of a DC bias voltage V on quantum interference
corrections to the measured differential conductance in metallic mesoscopic
wires and rings. The amplitude of both universal conductance fluctuations (UCF)
and Aharonov-Bohm effect (ABE) is enhanced several times for voltages larger
than the Thouless energy. The enhancement persists even in the presence of
inelastic electron-electron scattering up to V ~ 1 mV. For larger voltages
electron-phonon collisions lead to the amplitude decaying as a power law for
the UCF and exponentially for the ABE. We obtain good agreement of the
experimental data with a model which takes into account the decrease of the
electron phase-coherence length due to electron-electron and electron-phonon
scattering.Comment: New title, refined analysis. 7 pages, 3 figures, to be published in
Europhysics Letter
Vortex Viscosity in Magnetic Superconductors Due to Radiation of Spin Waves
In type-II superconductors that contain a lattice of magnetic moments,
vortices polarize the magnetic system inducing additional contributions to the
vortex mass, vortex viscosity, and vortex-vortex interaction. Extra magnetic
viscosity is caused by radiation of spin waves by a moving vortex. Like in the
case of Cherenkov radiation, this effect has a characteristic threshold
behavior and the resulting vortex viscosity may be comparable to the well-known
Bardeen-Stephen contribution. The threshold behavior leads to an anomaly in the
current-voltage characteristics, and a drop in dissipation for a current
interval that is determined by the magnetic excitation spectrum.Comment: 4 pages, 1 figur
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