Evidence for a quantum phase transition in electron-doped Pr2-xCexCuO4-delta from thermopower measurements

The evidence for a quantum phase transition under the superconducting dome in the high-T-c cuprates has been controversial. We report low-temperature normal state thermopower (S) measurements in electron-doped Pr2-xCexCuO4-delta as a function of doping (x from 0.11 to 0.19). We find that at 2 K both S and S/T increase dramatically from x=0.11 to 0.16 and then saturate in the overdoped region. This behavior has a remarkable similarity to previous Hall effect results in Pr2-xCexCuO4-delta. Our results are further evidence for an antiferromagnetic to paramagnetic quantum phase transition in electron-doped cuprates near x=0.16.