868 research outputs found
Rotating Fulde-Ferrell-Larkin-Ovchinnikov state in cold Fermi gases
We study an effect of rotation on the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)
state of two component Fermi superfluid gases in a toroidal trap. We
investigate a stability of the FFLO states in the quasi-one-dimensional regime
on the basis of the Bogoliubov-de Gennes equation. We find that two novel FFLO
phases, i.e., the half quantum vortex state and the intermediate state of
Fulde-Ferrell (FF) state and Larkin-Ovchinnikov (LO) state, are stabilized by
the rotation. The phase diagram for the FF state, LO state, intermediate state,
and half quantum vortex state is shown in both T-P plane and T-h plane. We
demonstrate characteristic features of these states, such as the order
parameter, flux quantization, and local polarization. Several related works are
discussed, and the advantages of cold Fermi gases are indicated.Comment: 10 pages, 9 figures. Accepted for publication in PRA; added
reference
Odd-parity superconductivity by competing spin-orbit coupling and orbital effect in artificial heterostructures
We show that odd-parity superconductivity occurs in multilayer Rashba systems
without requiring spin-triplet Cooper pairs. A pairing interaction in the
spin-singlet channel stabilizes the odd-parity pair-density-wave (PDW) state in
the magnetic field parallel to the two-dimensional conducting plane. It is
shown that the layer-dependent Rashba spin-orbit coupling and the orbital
effect play essential roles for the PDW state in binary and tricolor
heterostructures. We demonstrate that the odd-parity PDW state is a
symmetry-protected topological superconducting state characterized by the
one-dimensional winding number in the symmetry class BDI. The superconductivity
in the artificial heavy-fermion superlattice CeCoIn_5/YbCoIn_5 and bilayer
interface SrTiO_3/LaAlO_3 is discussed.Comment: To be published in Phys. Rev.
Pair-density wave states through spin-orbit coupling in multilayer superconductors
Spin singlet superconductors with quasi-two dimensional multilayer structure
are studied in high magnetic fields. Specifically we concentrate on bi- and
tri-layer systems whose layers by symmetry are subject Rashba-type spin-orbit
coupling. The combination of magnetic field and spin-orbit coupling leads to a
first order phase transition between different states of layer-dependent
superconducting order parameters upon rising the magnetic field. In this
context we distinguish the low-field Bardeen-Cooper-Schrieffer state where all
layers have order parameters of the same sign and the high-field pair-density
wave state where the layer-dependent order parameters change the sign at the
center layer. We also show that progressive paramagnetic limiting effects yield
additional features in the H-T phase diagram. As possible realizations of such
unusual superconducting phases we consider artificial superlattices of
CeCoIn_5, as well as some multilayer high-T_c cuprates.Comment: 7 pages, 6 figures. Accepted for publication in PR
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