High-Field Quasiparticle Tunneling in Bi_2Sr_2CaCu_2O_8+delta: Negative Magnetoresistance in the Superconducting State

TL;DR

This study investigates the c-axis resistivity in Bi-2212 under high magnetic fields, revealing how quasiparticle tunneling contributes to negative magnetoresistance and the behavior of the superconducting and normal states.

Contribution

It demonstrates the suppression of Josephson conductivity and the linear growth of quasiparticle conductivity with magnetic field in high-Tc cuprates.

Findings

Quasiparticle conductivity grows linearly with magnetic field.

Resistivity saturates at low temperatures, indicating scattering at d-gap nodes.

Superlinear conductivity signifies the normal state above T_c.

Abstract

We report on the c-axis resistivity rho_c(H) in Bi_2Sr_2CaCu_2O_{8+\delta} that peaks in quasi-static magnetic fields up to 60 T. By suppressing the Josephson part of the two-channel (Cooper pair/quasiparticle) conductivity \sigma_c (H), we find that the negative slope of \rho_c(H) above the peak is due to quasiparticle tunneling conductivity \sigma_q(H) across the CuO_2 layers below H_{c2}. At high fields (a) \sigma_q(H) grows linearly with H, and (b) \rho_c(T) tends to saturate (sigma_c \neq 0) as T->0, consistent with the scattering at the nodes of the d-gap. A superlinear sigma_q(H) marks the normal state above T_c.