Effects of the pseudo-gap on the field-induced kinetic energy density of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ single crystals

TL;DR

This study investigates how the pseudogap affects the field-induced kinetic energy density and superfluid density in Bi2212 cuprate superconductors, revealing their coexistence and relation to the pseudogap energy scale.

Contribution

It provides experimental evidence linking the pseudogap to the kinetic energy density and superfluid density, highlighting their coexistence in Bi2212 superconductors.

Findings

Kinetic energy density $E_k$ varies with the pseudogap in underdoped samples.

A peak in $E_k$ at hole doping $p\,\sim0.18$ relates to a van Hove singularity.

Superfluid density $ ho_s$ is also connected to the pseudogap energy scale.

Abstract

We report on magnetization experiments from which we obtain the field-induced kinetic energy density, $E_k$, in the superconducting phase of several Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ single crystal samples. The kinetic energy magnitude changes according to the characteristic reduction of the single-electron density of states produced by the pseudogap in the underdoped limit. Moreover, a remarkable peak of $E_k$ occurring at the specific holes density $p\sim0.18$ is related to a van Hove singularity due to the pseudogap closure. We also extracted the superfluid density, $\rho_s$. We conclude that $E_k$ and $\rho_s$ are related to the pseudogap energy scale. This result is understood as an evidence of the coexistence between superconductivity and the pseudogap phenomenon in the Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ cuprate compound.