9 research outputs found
Theory of surface spectroscopy for noncentrosymmetric superconductors
We study noncentrosymmetric superconductors with the tetrahedral ,
tetragonal , and cubic point group . The order parameter is computed
self-consistently in the bulk and near a surface for several different singlet
to triplet order parameter ratios. It is shown that a second phase transition
below is possible for certain parameter values. In order to determine the
surface orientation's effect on the order parameter suppression, the latter is
calculated for a range of different surface orientations. For selected
self-consistent order parameter profiles the surface density of states is
calculated showing intricate structure of the Andreev bound states (ABS) as
well as spin polarization. The topology's effect on the surface states and the
tunnel conductance is thoroughly investigated, and a topological phase diagram
is constructed for open and closed Fermi surfaces showing a sharp transition
between the two for the cubic point group .Comment: 19 pages, 15 figures, accepted for publication in Phys. Rev.
Response, relaxation and transport in unconventional superconductors
We investigate the collision-limited electronic Raman response and the
attenuation of ultrasound in spin-singlet d-wave superconductors at low
temperatures. The dominating elastic collisions are treated within a t-matrix
approximation, which combines the description of weak (Born) and strong
(unitary) impurity scattering. In the long wavelength limit a two-fluid
description of both response and transport emerges. Collisions are here seen to
exclusively dominate the relaxational dynamics of the (Bogoliubov)
quasiparticle system and the analysis allows for a clear connection of response
and transport phenomena. When applied to quasi-2-d superconductors like the
cuprates, it turns out that the transport parameter associated with the Raman
scattering intensity for B1g and B2g photon polarization is closely related to
the corresponding components of the shear viscosity tensor, which dominates the
attenuation of ultrasound. At low temperatures we present analytic solutions of
the transport equations, resulting in a non-power-law behavior of the transport
parameters on temperature.Comment: 22 pages, 3 figure