Low-Lying Quasiparticle Excitations around a Vortex Core in Quantum Limit

Abstract

Focusing on a quantum-limit behavior, we study a single vortex in a clean $s$-wave type-II superconductor by self-consistently solving the Bogoliubov--de Gennes equation. The discrete energy levels of the vortex bound states in the quantum limit are discussed. The vortex core radius shrinks monotonically up to an atomic-scale length on lowering the temperature $T$, and the shrinkage stops to saturate at a lower $T$. The pair potential, supercurrent, and local density of states around the vortex exhibit Friedel-like oscillations. The local density of states has particle-hole asymmetry induced by the vortex. These are potentially observed directly by scanning tunneling microscopy.