3 research outputs found
Non-Fermi liquid fixed point for an imbalanced gas of fermions in dimensions
We consider a gas of two species of fermions with population imbalance. Using
the renormalization group in dimensions, we show that for
spinless fermions and a fixed point appears at finite attractive
coupling where the quasiparticle residue vanishes, and identify this with the
transition to Larkin--Ovchinnikov--Fulde--Ferrell order (inhomogeneous
superconductivity). When the two species of fermions also carry spin degrees of
freedom we find a fixed point indicating a transition to spin density wave
order.Comment: 4 pages and 4 figure
The phase diagram of 2D polar condensates in a magnetic field
Spin one condensates in the polar (antiferromagnetic) phase in two dimensions
are shown to undergo a transition of the Ising type, in addition to the
expected Kosterlitz--Thouless (KT) transition of half vortices, due to the
quadratic Zeeman effect. We establish the phase diagram in terms of temperature
and the strength of the Zeeman effect using Monte Carlo simulations. When the
Zeeman effect is sufficiently strong the Ising and KT transitions merge. For
very strong Zeeman field the remaining transition is of the familiar integer KT
type.Comment: 4 pages, 7 figure
Coarsening Kinetics of a Two Dimensional O(2) Ginzburg-Landau Model: Effect of Reversible Mode Coupling
We investigate, via numerical simulations, the phase ordering kinetics of a
two- dimensional soft-spin O(2) Ginzburg-Landau model when a reversible mode
cou- pling is included via the conserved conjugate momentum of the spin order
parameter (the model E). Coarsening of the system, when quenched from a dis-
ordered state to zero temperature, is observed to be enhanced by the existence
of the mode coupling terms. The growth of the characteristic length scale L(t)
exhibits an effective super-diffusive growth exponent that can be interpreted
as a positive logarithmic-like correction to a diffusive growth, i.e., L(t) ~
(t ln t)^{1/2}. In order to understand this behavior, we introduced a simple
phenomenological model of coarsening based on the annihilation dynamics of a
vortex-antivortex pair, incorporating the effect of vortex inertia and
logarithmically divergent mobility of the vortex. With a suitable choice of the
parameters, numerical solutions of the simple model can fit the full simulation
results very adequately. The effective growth exponent in the early time stage
is larger due to the effect of the vortex inertia, which crosses over into late
time stage characterized by positive logarithmic correction to a diffusive
growth. We also investigated the non-equilibrium autocorrelation function from
which the so called {\lambda} exponent can be extracted. We get {\lambda} =
1.99(2) which is distinctively larger than the value of {\lambda} = 1.17 for
the purely dissipative model-A dynamics of non-conserved O(2) models.Comment: 19 pages, 8 figure