Theory of surface Andreev bound states and tunneling spectroscopy in three-dimensional chiral superconductors

TL;DR

This paper analyzes surface Andreev bound states and tunneling spectroscopy in 3D chiral superconductors, revealing how magnetic fields influence conductance features and proposing methods to identify pairing symmetries.

Contribution

It provides analytical formulas for SABS energy dispersion in 3D chiral superconductors and extends tunneling conductance models to include spin-triplet non-unitary pairings.

Findings

Zero bias conductance dip can turn into a peak under magnetic field.

Analytical SABS dispersion formulas for pair potentials with point and line nodes.

Magneto tunneling spectroscopy helps identify pairing symmetry in UPt3.

Abstract

We study the surface Andreev bound states (SABSs) and quasiparticle tunneling spectroscopy of three-dimensional (3D) chiral superconductor by changing the surface (interface) misorientation angle of chiral superconductors. We obtain analytical formula of the energy dispersion of SABS for general pair potential when an original 4$\times$4 BdG Hamiltonian can be reduced to be two 2$\times$2 blocks. The resulting SABS for 3D chiral superconductors with pair potential given by $k_z(k_x + ik_y)^{\nu}$ $({\nu} = 1, 2)$ has a complicated energy dispersion due to the coexistence of both point and line nodes. We focus on the tunneling spectroscopy of this pairing in the presence of applied magnetic field which induces Doppler shift of quasiparticle spectra. By contrast to previous known Doppler effect in unconventional superconductors, zero bias conductance dip can change into zero bias conductance peak by external magnetic field. We also study SABSs and tunneling spectroscopy for possible pairing symmetries of UPt$_3$ . For this purpose, we extend a standard formula of tunneling conductance of unconventional superconductor junctions in order to treat spin-triplet non-unitary pairings. The magneto tunneling spectroscopy, i.e., tunneling spectroscopy in the presence of magnetic field, can serve as a guide to determine the pairing symmetry of this material.