Electromagnetic response in kinetic energy driven cuprate superconductors: Linear response approach

TL;DR

This paper investigates the electromagnetic response of cuprate superconductors within a kinetic energy driven framework, analyzing magnetic field profiles, penetration depth, and superfluid density using a linear response approach.

Contribution

It introduces a linear response method to study electromagnetic properties in cuprate superconductors based on kinetic energy driven superconductivity, addressing gauge invariance issues.

Findings

Magnetic field decays exponentially at the surface at low temperatures.

Penetration depth varies linearly with temperature, with deviations at very low temperatures.

Superfluid density decreases linearly with doping in the underdoped regime.

Abstract

Within the framework of the kinetic energy driven superconductivity, the electromagnetic response in cuprate superconductors is studied in the linear response approach. The kernel of the response function is evaluated and employed to calculate the local magnetic field profile, the magnetic field penetration depth, and the superfluid density, based on the specular reflection model for a purely transverse vector potential. It is shown that the low temperature magnetic field profile follows an exponential decay at the surface, while the magnetic field penetration depth depends linearly on temperature, except for the strong deviation from the linear characteristics at extremely low temperatures. The superfluid density is found to decrease linearly with decreasing doping concentration in the underdoped regime. The problem of gauge invariance is addressed and an approximation for the dressed current vertex, which does not violate local charge conservation is proposed and discussed.