Spectroscopic signatures of the Larkin-Ovchinnikov state in the conductance characteristics of a normal-metal/superconductor junction

TL;DR

This paper predicts distinctive spectroscopic signatures in conductance spectra caused by the Larkin-Ovchinnikov state in a normal-metal/superconductor junction, highlighting features like zero-energy bound states and a midgap band.

Contribution

It introduces a discrete-lattice calculation of conductance spectra revealing unique signatures of the LO state in N/S junctions, including midgap states and anisotropic features.

Findings

Zero-energy Andreev bound states form around nodal lines.

A hybridized midgap-states band appears due to periodic nodal lines.

Distinctive spectral features differentiate the LO state from BCS and FF states.

Abstract

Using a discrete-lattice approach, we calculate the conductance spectra between a normal metal and an s-wave Larkin-Ovchinnikov (LO) superconductor, with the junction interface oriented {\em along} the direction of the order-parameter (OP) modulation. The OP sign reversal across one single nodal line can induce a sizable number of zero-energy Andreev bound states around the nodal line, and a hybridized midgap-states band is formed amid a momentum-dependent gap as a result of the periodic array of nodal lines in the LO state. This band-in-gap structure and its anisotropic properties give rise to distinctive features in both the point-contact and tunneling spectra as compared with the BCS and Fulde-Ferrell cases. These spectroscopic features can serve as distinguishing signatures of the LO state.