Quantum Phase Transitions in a Cuprate Superconductor Bi_{2}Sr_{2-x}La_{x}CuO_{6+\delta}

TL;DR

This study investigates quantum phase transitions in a cuprate superconductor by measuring charge and heat transport properties across various doping levels, revealing two distinct QPTs in the material's superconducting regime.

Contribution

The paper provides experimental evidence for two quantum phase transitions in Bi_{2}Sr_{2-x}La_{x}CuO_{6+ extdelta} through low-temperature transport measurements, expanding understanding of its phase diagram.

Findings

Signatures of a QPT at 1/8 hole doping.

Evidence of a second QPT at optimal doping.

Transport properties indicate multiple QPTs in the superconducting regime.

Abstract

To elucidate a quantum phase transition (QPT) in Bi_2Sr_{2-x}La_xCuO_{6+\delta}, we measure charge and heat transport properties at very low temperatures and examine the following characteristics for a wide range of doping: normal-state resistivity anisotropy under 58 T, temperature dependence of the in-plane thermal conductivity K_{ab}, and the magnetic-field dependence of K_{ab}. It turns out that all of them show signatures of a QPT at the 1/8 hole doping. Together with the recent normal-state Hall measurements under 58 T that signified the existence of a QPT at optimum doping, the present results indicate that there are two QPTs in the superconducting doping regime of this material.