Enigma of the vortex state in a strongly correlated d-wave superconductor

TL;DR

This paper investigates how strong electronic correlations in d-wave superconductors cause the vortex core to transition from metallic to Mott-insulating as doping decreases, revealing non-monotonic vortex size and critical field behavior.

Contribution

It demonstrates the doping-dependent transformation of vortex cores in strongly correlated superconductors and explains experimental observations in cuprates.

Findings

Vortex core changes from metallic to Mott-insulating with underdoping

Vortex size varies non-monotonically with doping

Critical field Hc2 shows similar non-monotonic behavior

Abstract

We show that strong electronic repulsion transforms a vortex core from a metallic-type in overdoped regime to a Mott-insulator at underdoping of a strongly correlated d-wave superconductor. This changeover is accompanied by an accumulation of electron density at the vortex core towards local half-filling in the underdoped region, which in turn facilitates the formation of the Mott insulating core. We find that the size of vortices evolves non-monotonically with doping. A similar non-monotonicity of critical field $H_{\rm c2}$, as extracted from superfluid stiffness, is also found. Our results explain some recent experimental puzzles of cuprate superconductors.