Vortex bound state of Kondo lattice coupled to compensated metal

TL;DR

This paper investigates the unique properties of vortex bound states in a Kondo lattice superconductor coupled to a compensated metal, revealing unconventional features distinct from traditional s-wave superconductors through numerical and analytical methods.

Contribution

It introduces a comprehensive theoretical framework combining numerical BdG solutions and quasiclassical Green's functions to analyze vortex bound states in Kondo lattice superconductors.

Findings

Vortex core states have a length scale independent of interaction strength.

Core bound state energy is comparable to the bulk gap.

Properties are linked to odd frequency dependence of self-energies.

Abstract

We theoretically study physical properties of the low-energy quasiparticle excitations at the vortex core in the full-gap superconducting state of the Kondo lattice coupled to compensated metals. Based on the mean-field description of the superconducting state, we numerically solve the Bogoliubov-de Gennes (BdG) equations for the tight-binding Hamiltonian. The isolated vortex is characterized by a length scale independent of the magnitude of the interaction and the energy level of the core bound state is the same order as the bulk gap. These properties are in strong contrast to the conventional s-wave superconductor. To gain further insights, we also consider the effective Hamiltonian in the continuous limit and construct the theoretical framework of the quasiclassical Green's function of conduction electrons. With the use of the Kramer-Pesch approximation, we analytically derive the spectral function describing the quasiparticle excitations which is consistent with the numerics. It has been revealed that the properties of the vortex bound state are closely connected to the characteristic odd frequency dependence of both the normal and anomalous self-energies which is proportional to the inverse of frequency.