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

Abstract

To elucidate a quantum phase transition (QPT) in Bi_2Sr_{2-x}La_xCuO_{6+δ}, 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.

4 pages, 3 figures; final version accepted for publication in Phys. Rev. Lett.; some references are added and experimental details are clarified