2,753 research outputs found
The effect of nonmagnetic impurities on the local density of states in s-wave superconductors
We study the effect of nonmagnetic impurities on the local density of states
(LDOS) in s-wave superconductors. The quasiclassical equations of
superconductivity are solved selfconsistently to show how LDOS evolves with
impurity concentration. The spatially averaged zero-energy LDOS is a linear
function of magnetic induction in low fields, N(E=0)=cB/H_{c2}, for all
impurity concentration. The constant of proportionality "c" depends weakly on
the electron mean free path. We present numerical data for differential
conductance and spatial profile of zero-energy LDOS which can help in
estimating the mean free path through the LDOS measurement.Comment: 7 pages, 7 figures (high quality color figure available on request
Saturation of Magnetorotational Instability through Magnetic Field Generation
The saturation mechanism of Magneto-Rotational Instability (MRI) is examined
through analytical quasilinear theory and through nonlinear computation of a
single mode in a rotating disk. We find that large-scale magnetic field is
generated through the alpha effect (the correlated product of velocity and
magnetic field fluctuations) and causes the MRI mode to saturate. If the
large-scale plasma flow is allowed to evolve, the mode can also saturate
through its flow relaxation. In astrophysical plasmas, for which the flow
cannot relax because of gravitational constraints, the mode saturates through
field generation only.Comment: 9 pages, 10 figures to appear in ApJ, Jun 2009, 10 v69
Bernoulli potential in type-I and weak type-II superconductors: III. Electrostatic potential above the vortex lattice
The electrostatic potential above the Abrikosov vortex lattice, discussed
earlier by Blatter {\em et al.} {[}PRL {\bf 77}, 566 (1996){]}, is evaluated
within the Ginzburg-Landau theory. Unlike previous studies we include the
surface dipole. Close to the critical temperature, the surface dipole reduces
the electrostatic potential to values below a sensitivity of recent sensors. At
low temperatures the surface dipole is less effective and the electrostatic
potential remains observable as predicted earlier.Comment: 8 pages 5 figure
Cyclic phase in F=2 spinor condensate: Long-range order, kinks, and roughening transition
We study the effect of thermal fluctuations on homogeneous infinite
Bose-Einstein condensate with spin F=2 in the cyclic state, when atoms occupy
three hyperfine states with . We use both the approach of
small-amplitude oscillations and mapping of our model on the sine-Gordon model.
We show that thermal fluctuations lead to the existence of the rough phase in
one- and two-dimensional systems, when presence of kinks is favorable. The
structure and energy of a single kink are found. We also discuss the effect of
thermal fluctuations on spin degrees of freedom in F=1 condensate.Comment: 6 pages, 1 figure; final version, accepted for publication in Phys.
Rev.
Majorana bound state in rotating superfluid 3He-A between parallel plates
A concrete and experimentally feasible example for testing the putative
Majorana zero energy state bound in a vortex is theoretically proposed for a
parallel plate geometry of superfluid He-A phase. We examine the
experimental setup in connection with ongoing rotating cryostat experiments.
The theoretical analysis is based on the well-established Ginzburg--Landau
functional, supplemented by microscopic calculations of the Bogoliubov--de
Gennes equation, both of which allow the precise location of the parameter
regions of the Majorana state to be found in realistic situations.Comment: 5 pages, 4 figure
Vortex structures and zero energy states in the BCS-to-BEC evolution of p-wave resonant Fermi gases
Multiply quantized vortices in the BCS-to-BEC evolution of p-wave resonant
Fermi gases are investigated theoretically. The vortex structure and the
low-energy quasiparticle states are discussed, based on the self-consistent
calculations of the Bogoliubov-de Gennes and gap equations. We reveal the
direct relation between the macroscopic structure of vortices, such as particle
densities, and the low-lying quasiparticle state. In addition, the net angular
momentum for multiply quantized vortices with a vorticity is found to
be expressed by a simple equation, which reflects the chirality of the Cooper
pairing. Hence, the observation of the particle density depletion and the
measurement of the angular momentum will provide the information on the
core-bound state and -wave superfluidity. Moreover, the details on the zero
energy Majorana state are discussed in the vicinity of the BCS-to-BEC
evolution. It is demonstrated numerically that the zero energy Majorana state
appears in the weak coupling BCS limit only when the vortex winding number is
odd. There exist the branches of the core bound states for a vortex
state with vorticity , whereas only one of them can be the zero energy.
This zero energy state vanishes at the BCS-BEC topological phase transition,
because of interference between the core-bound and edge-bound states.Comment: 15 pages, 9 figures, published versio
Spontaneous mass current and textures of p-wave superfluids of trapped Fermionic atom gases at rest and under rotation
It is found theoretically based on the Ginzburg-Landau framework that p-wave
superfluids of neutral atom gases in three dimension harmonic traps exhibit
spontaneous mass current at rest, whose direction depends on trap geometry.
Under rotation various types of the order parameter textures are stabilized,
including Mermin-Ho and Anderson-Toulouse-Chechetkin vortices. In a cigar shape
trap spontaneous current flows longitudial to the rotation axis and thus
perpendicular to the ordinary rotational current. These features, spontaneous
mass current at rest and texture formation, can be used as diagnoses for p-wave
superfluidity.Comment: 5 pages, 5 figure
Stability of half quantum vortex in rotating superfluid 3He-A between parallel plates
We have found the precise stability region of the half quantum vortex (HQV)
for superfluid He A phase confined in parallel plates with a narrow gap
under rotation. Standard Ginzburg-Landau free energy, which is well
established, is solved to locate the stability region spanned by temperature
and rotation speed (). This - stability region is wide
enough to check it experimentally in available experimental setup. The detailed
order parameter structure of HQV characterized by A core is given to
facilitate the physical reasons of its stability over other vortices or
textures.Comment: 5 pages, 4 figure
Majorana surface states of superfluid 3He A- and B-phases in a slab
Motivated by experiments on the superfluid 3He confined in a thin slab, we
design a concrete experimental setup for observing the Majorana surface states.
We solve the quasi-classical Eilenberger equation, which is quantitatively
reliable, to evaluate several quantities, such as local density of states
(LDOS), mass current for the A-phase, and spin current for the B-phase. In
connection with realistic slab samples, we consider the upper and lower
surfaces and the side edges including the corners with several thicknesses.
Consequently the influence on the Majorana zero modes from the spatial
variation of l-vector for the A-phase in thick slabs and the energy splitting
of the zero-energy quasi-particles for the B-phase confined in thin slabs are
demonstrated. The corner of slabs in the B-phase is accompanied by the unique
zero-energy LDOS of corner modes. On the basis of the quantitative calculation,
we propose several feasible and verifiable experiments to check the existence
of the Majorana surface states, such as the measurement of specific heat, edge
current, and anisotropic spin susceptibility.Comment: 13 pages, 10 figures, published versio
- …