Intervortex quasiparticle tunneling and electronic structure of multi-vortex configurations in type-II superconductors

TL;DR

This paper investigates how quasiparticle tunneling between vortex cores in type-II superconductors influences their electronic spectra, revealing a transition in spectral branches and oscillations in the density of states that could be experimentally observed.

Contribution

It introduces a detailed analysis of quasiparticle tunneling effects on multi-vortex spectra, highlighting a transition from degenerate to anomalous spectral branches.

Findings

Formation of strongly coupled quasiparticle states for small intervortex distances

Transition from degenerate to anomalous spectral branches

Oscillatory behavior of the density of states at the Fermi level

Abstract

The electronic spectrum of multi-vortex configurations in type-II superconductors is studied taking account of the effect of quasiparticle tunneling between the vortex cores. The tunneling is responsible for the formation of strongly coupled quasiparticle states for intervortex distances $a<a_c$, where the critical distance $a_c$ is of the order of several coherence lengths $\xi$. Analyzing the resulting spectra of vortex clusters bonded by the quasiparticle tunneling we find a transition from a set of degenerate Caroli - de Gennes - Matricon branches to anomalous branches similar to the ones in multi-quanta giant vortices. This spectrum transformation results in the oscillatory behavior of the density of states at the Fermi level as a function of $a$ and could be observed in mesoscopic superconductors and disordered flux line arrays in the bulk systems.