3,678 research outputs found
Nonuniform mixed-parity superfluid state in Fermi gases
We study the effects of dipole interaction on the superfluidity in a
homogeneous Fermi gas with population imbalance. We show that the
Larkin-Ovchinnikov-Fulde-Ferrell phase is replaced by another nonuniform
superfluid phase, in which the order parameter has a nonzero triplet component
induced by the dipole interaction.Comment: 4 pages, 1 figur
Recent developments in unconventional superconductivity theory
The review of recent developments in the unconventional superconductivity
theory is given. In the fist part I consider the physical origin of the Kerr
rotation polarization of light reflected from the surface of superconducting
. Then the comparison of magneto-optical responses in
superconductors with orbital and spin spontaneous magnetization is presented.
The latter result is applied to the estimation of the magneto-optical
properties of neutral superfluids with spontaneous magnetization. The second
part is devoted to the natural optical activity or gyrotropy properties of
noncentrosymmetric metals in their normal and superconducting states. The
temperature behavior of the gyrotropy coefficient is compared with the
temperature behavior of paramagnetic susceptibility determining the noticeable
increase of the paramagnetic limiting field in noncentrosymmetric
superconductors. In the last chapter I describe the order parameter and the
symmetry of superconducting state in the itinerant ferromagnet with
orthorhombic symmetry. Finally the Josephson coupling between two adjacent
ferromagnet superconducting domains is discussed.Comment: 15 page
FFLO state in thin superconducting films
We present the analysis of the inhomogeneous Fulde-Ferrell-Larkin-Ovchinnikov
(FFLO) superconducting state in thin superconducting films in the parallel
magnetic field. For the tetragonal crystal symmetry (relevant to CeCoIn -
the most probable candidate for the FFLO state formation) we predict a very
peculiar in-plane angular dependence of the FFLO critical field due to the
orbital effect. In the uniform superconducting state the critical field should
be isotropic. The magnetic field pins also the direction of the FFLO modulation
permitting thus to study the critical current anisotropy. Our calculations
reveal a strong critical current anisotropy in the FFLO state in sharp contrast
with the usual superconducting state. The predicted characteristic anisotropies
of the critical field and critical current may provide an unambiguous probe of
the FFLO phase formation.Comment: 7 pages, 2 figures, to be published in Europhys. Let
Interplay of paramagnetic, orbital and impurity effects on the phase transition of a normal metal to superconducting state
We derive the generalized Ginzburg-Landau free energy functional for
conventional and unconventional singlet superconductors in the presence of
paramagnetic, orbital and impurity effects. Within the mean field theory, we
determine the criterion for appearence of the non uniform
(Fulde-Ferrell-Larkin-Ovchinnikov) superconducting state, with vortex lattice
structure and additional modulation along the magnetic field. We also discuss
the possible change of the order of transition from normal to superconducting
state. We find that the superconducting phase diagram is very sensitive to
geometrical effects such as the nature of the order parameter and the shape of
the Fermi surface. In particular, we obtain the qualitative phase diagrams for
three-dimensional isotropic s-wave superconductors and in quasi two-dimensional
d-wave superconductors under magnetic field perpendicular to the conducting
layers.
In addition, we determine the criterion for instability toward non uniform
superconducting state in s-wave superconductors in the dirty limit.Comment: 15 pages, 4 figure
Reply to "Comment on "Domain Structure in a Superconducting Ferromagnet""
This short article is a reply to the comment from E.B. Sonin on our paper on
the domain structure in a superconducting ferromagnet published in Phys. Rev.
Lett..Comment: 1 page, accepted for publication in Phys. Rev. Let
Odd spin-triplet superconductivity in a multilayered superconductor-ferromagnet Josephson junction
We study the dc Josephson effect in a diffusive multilayered SF'FF'S
structure, where S is a superconductor and F,F' are different ferromagnets. We
assume that the exchange energies in the F' and F layers are different (
and , respectively) and the middle F layer consists of two layers with
parallel or antiparallel magnetization vectors . The vectors in the left
and right F' layers are generally not collinear to those in the F layer. In the
limit of a weak proximity effect we use a linearized Usadel equation. Solving
this equation, we calculate the Josephson critical current for arbitrary
temperatures, arbitrary thicknesses of the F' and F layers ( and
) in the case of parallel and antiparallel orientations in the F
layer. The part of the critical current formed by the short-range
(SRC) singlet and S=0 triplet condensate components decays on a short length
, whereas the part due to the long-range
triplet component (LRTC) decreases with increasing on the
length . Our results are in agreement with the
experiment \cite{Birge}.Comment: 13 pages, 6 figures; some references updated and adde
Electrodynamics of Fulde-Ferrell-Larkin-Ovchinnikov superconducting state
We develop the Ginzburg-Landau theory of the vortex lattice in clean
isotropic three-dimensional superconductors at large Maki parameter, when
inhomogeneous Fulde-Ferrell-Larkin-Ovchinnikov state is favored. We show that
diamagnetic superfluid currents mainly come from paramagnetic interaction of
electron spins with local magnetic field, and not from kinetic energy response
to the external field as usual. We find that the stable vortex lattice keeps
its triangular structure as in usual Abrikosov mixed state, while the internal
magnetic field acquires components perpendicular to applied magnetic field.
Experimental possibilities related to this prediction are discussed.Comment: 5 pages, 1 figur
Charged-Surface Instability Development in Liquid Helium; Exact Solutions
The nonlinear dynamics of charged-surface instability development was
investigated for liquid helium far above the critical point. It is found that,
if the surface charge completely screens the field above the surface, the
equations of three-dimensional (3D) potential motion of a fluid are reduced to
the well-known equations describing the 3D Laplacian growth process. The
integrability of these equations in 2D geometry allows the analytic description
of the free-surface evolution up to the formation of cuspidal singularities at
the surface.Comment: latex, 5 pages, no figure
Odd triplet superconductivity in a superconductor/ferromagnet structure with a spiral magnetic structure
We analyze a superconductor-ferromagnet (S/F) system with a spiral magnetic
structure in the ferromagnet F for a weak and strong exchange field. The
long-range triplet component (LRTC) penetrating into the ferromagnet over a
long distance is calculated for both cases. In the dirty limit (or weak
ferromagnetism) we study the LRTC for conical ferromagnets. Its spatial
dependence undergoes a qualitative change as a function of the cone angle
\theta. At small angles the LRTC decays in the ferromagnet exponentially in a
monotonic way. If the angle \theta exceeds a certain value, the exponential
decay of the LRTC is accompanied by oscillations with a period that depends on
\theta. This oscillatory behaviour leads to a similar dependence of the
Josephson critical current in SFS junctions on the thickness of the F layer. In
the case of a strong ferromagnet the LRTC decays over the length which is
determined by the wave vector of the magnetic spiral and by the exchange field.Comment: 15 pages, 4 figures; to be published in Phys. Rev. B 73 (10) (2006
On the spin susceptibility of noncentrosymmetric superconductors
We calculate the spin susceptibility of a superconductor without inversion
symmetry, both in the clean and disordered cases. The susceptibility has a
large residual value at zero temperature, which is further enhanced in the
presence of scalar impurities.Comment: 12 pages, 3 figure
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