Talk Title: Signatures of Larkin-Ovchinnikov State via Hybridized
Midgap Band States When a spin-singlet superconductor is subjected to a sufficiently strong
Zeeman field, the Fermi surfaces of spin-up and -down electrons will split and
some Cooper pairs of the BCS state tend to break up. Fulde and Ferrell (FF),
and Larkin and Ovchinnikov (LO) proposed independently a new superconducting
state with periodically varying phase or sign of the order parameter (OP),
respectively. Though there have been experiments suggestive of its existence in
various superconductors, direct evidence of the periodic sign reversal of the
OP is still desirable. Here we show that a hybridized midgap states band,
formed inside the gap of the superconductor by Andreev reflections around the
periodically spaced nodal lines of the OP of the LO state, can produce
distinctive features in both the point-contact and tunneling conductance
spectra. These spectroscopic features can serve as distinguishing signatures of
the LO state. |