Quantum Phase Transition In The Magnetic-field-induced Normal State Of Optimum-doped High-t_c Cuprate Superconductors At Low Temperatures

摘要

A 60 T magnetic field suppresses the superconducting transition temperature T_c in La_(2-p)Sr_pCuO_4 to reveal a Hall number anomaly, which develops only at temperatures below zero-field T_c and peaks at the exact location of p that maximizes T_c. The anomaly bears a striking resemblance to observations in Bi_2Sr_(2-x)La_xCuO_(6+δ), suggesting a normal-state phenomenology common to the cuprates that underlies the high-temperature superconducting phase. The peak is ascribed to a Fermi surface reconstruction at a quantum phase transition near optimum doping that is coincident with the collapse of the pseudogap state.