Local density of states in the vortex lattice in a type II superconductor

TL;DR

This paper investigates the local density of states in a vortex lattice of a type II superconductor using quasi-classical theory, revealing how LDOS patterns evolve with magnetic field strength and match experimental observations.

Contribution

It provides a detailed theoretical analysis of LDOS structures in vortex lattices, especially for NbSe_2, highlighting the transition from cylindrical to star-shaped patterns at different fields.

Findings

LDOS shows cylindrical structure at low fields

LDOS becomes sixfold star-shaped at high fields

Star orientation matches experimental STM data

Abstract

Local density of states (LDOS) in the triangular vortex lattice is investigated based on the quasi-classical Eilenberger theory. We consider the case of an isotropic s-wave superconductor with the material parameter appropriate to NbSe_2. At a weak magnetic field, the spatial variation of the LDOS shows cylindrical structure around a vortex core. On the other hand, at a high field where the core regions substantially overlap each other, the LDOS is sixfold star-shaped structure due to the vortex lattice effect. The orientation of the star coincides with the experimental data of the scanning tunneling microscopy. That is, the ray of the star extends toward the nearest-neighbor (next nearest-neighbor) vortex direction at higher (lower) energy.