259 research outputs found
Split degenerate states and stable p+ip phases from holography
In this paper, we investigate the p+p superfluid phases in the complex
vector field holographic p-wave model. We find that in the probe limit, the
p+p phase and the p-wave phase are equally stable, hence the p and p
orders can be mixed with an arbitrary ratio to form more general p+p
phases, which are also equally stable with the p-wave and p+p phases. As a
result, the system possesses a degenerate thermal state in the superfluid
region. We further study the case with considering the back reaction on the
metric, and find that the degenerate ground states will be separated into
p-wave and p+p phases, and the p-wave phase is more stable. Finally, due to
the different critical temperature of the zeroth order phase transitions from
p-wave and p+p phases to the normal phase, there is a temperature region
where the p+p phase exists but the p-wave phase doesn't. In this region we
find the stable p+p phase for the first time.Comment: 16 pages, 5 figures; typos correcte
A thermal quench induces spatial inhomogeneities in a holographic superconductor
Holographic duality is a powerful tool to investigate the far-from
equilibrium dynamics of superfluids and other phases of quantum matter. For
technical reasons it is usually assumed that, after a quench, the far-from
equilibrium fields are still spatially uniform. Here we relax this assumption
and study the time evolution of a holographic superconductor after a
temperature quench but allowing spatial variations of the order parameter. Even
though the initial state and the quench are spatially uniform we show the order
parameter develops spatial oscillations with an amplitude that increases with
time until it reaches a stationary value. The free energy of these
inhomogeneous solutions is lower than that of the homogeneous ones. Therefore
the former corresponds to the physical configuration that could be observed
experimentally.Comment: corrected typos, added references and new results for a different
quenc
Characteristic length of a Holographic Superconductor with -wave gap
After the discovery of the -wave and -wave holographic superconductors,
holographic models of -wave superconductor have also been constructed
recently. We study analytically the perturbation of the dual gravity theory to
calculate the superconducting coherence length of the -wave
holographic superconductor near the superconducting phase transition point. The
superconducting coherence length divergents as near
the critical temperature . We also obtain the magnetic penetration depth
by adding a small external homogeneous magnetic
field. The results agree with the -wave and -wave models, which are also
the same as the Ginzburg-Landau theory.Comment: last version, 10 pages, accepted by PR
Normal modes and time evolution of a holographic superconductor after a quantum quench
We employ holographic techniques to investigate the dynamics of the order
parameter of a strongly coupled superconductor after a perturbation that drives
the system out of equilibrium. The gravity dual that we employ is the Soliton background at zero temperature. We first analyze the normal
modes associated to the superconducting order parameter which are purely real
since the background has no horizon. We then study the full time evolution of
the order parameter after a quench. For sufficiently a weak and slow
perturbation we show that the order parameter undergoes simple undamped
oscillations in time with a frequency that agrees with the lowest normal model
computed previously. This is expected as the soliton background has no horizon
and therefore, at least in the probe and large limits considered, the
system will never return to equilibrium. For stronger and more abrupt
perturbations higher normal modes are excited and the pattern of oscillations
becomes increasingly intricate. We identify a range of parameters for which the
time evolution of the order parameter become quasi chaotic. The details of the
chaotic evolution depend on the type of perturbation used. Therefore it is
plausible to expect that it is possible to engineer a perturbation that leads
to the almost complete destruction of the oscillating pattern and consequently
to quasi equilibration induced by superposition of modes with different
frequencies.Comment: 10 pages, 7 figures, corrected typos, expanded section on chaotic
oscillations and new results for other quenc
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