Reduction of the Superfluid Density in the Vortex-Liquid Phase of Bi2Sr2CaCu2Oy

TL;DR

This study investigates how the superfluid density in a Bi2Sr2CaCu2Oy superconductor decreases during the vortex-liquid phase, revealing electronic structure changes associated with vortex lattice melting.

Contribution

It provides new insights into the electronic structure changes occurring at the vortex melting transition in high-temperature superconductors.

Findings

Superfluid density decreases rapidly above the vortex-lattice melting transition.

Surface reactance increases significantly above the transition field.

Electronic structure is affected by vortex lattice melting, not just vortex pinning.

Abstract

In-plane complex surface impedance of a Bi2Sr2CaCu2Oy single crystal was measured in the mixed state at 40.8 GHz.The surface reactance, which is proportional to the real part of the effective penetration depth, increased rapidly just above the first-order vortex-lattice melting transition field and the second magnetization peak field.This increase is ascribed to the decrease in the superfluid density rather than the loss of pinning.This result indicates that the vortex melting transition changes the electronic structure as well as the vortex structure.