Fig. 5.
Phase competition in LSCO near the QCP at x = 0.06. (A) The Hall resistivity at T = 0.4 K as a function of the magnetic field, in several representative pixels from the COMBE library under study. (B) The doping dependence of Tc (red diamonds, left scale) and of BCG (blue circles, right scale), the field above which hysteretic switching appears. The fact that erratic switching is observed in every pixel, with the systematic doping dependence, is yet another proof that it is intrinsic to LSCO doped in the vicinity of the QCP. (C) The B-T-x phase diagram determined from the measurements on the entire combinatorial library. The CCG state evolves from the insulator state as the temperature T decreases (the phase boundary is denoted by the dashed lines). The CCG state and the superconductor state (SC) compete for the ground state at zero temperature. By decreasing the doping level x or increasing the applied magnetic field B, LSCO undergoes a quantum phase transition from the SC state to the CCG state.