Quantum Phase Transitions in a Cuprate Superconductor   Bi_{2}Sr_{2-x}La_{x}CuO_{6+\delta}
  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. 
Yoichi Ando, S. Ono, X. F. Sun, J. Takeya (CRIEPI), F. F. Balakirev,   J. B. Betts, G. S. Boebinger (LANL)