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.