Joint features of pressure effects and specific heat of RBa2Cu3Ox at distinct nh values

Abstract Investigations of specific heat and T c under pressure are presented for YBa 2 Cu 3 O x (Y123), NdBa 2 Cu 3 O x (Nd123) and Y 1−y Ca y Ba 2 Cu 3 O x (YCa123) for various oxygen contents. In Y123, at the maximum of the specific-heat jump ΔC/T c the pressure dependence of the transition temperature dT c /dp shows a zero crossing. Inversely, at the maximum of dT c /dp the jump in the specific heat becomes minimal. With Ca doping these joint features shift to lower oxygen contents x, whereas Nd123 causes a shift into the opposite direction. Considering the hole doping by Ca and the larger chain fragmentation in Nd123, we rescaled our results with respect to the hole content n h in the CuO 2 planes. In this plot features coalesce in two fixed hole concentrations, n h ≈0.11 and n h 0.17, irrespective of the substitution and doping. The maximum in ΔC/T c may be related to the appearance of a quantum critical point due to the disappearance of a pseudogap for hole contents above n h ≈0.17. The features at n h ≈0.11 point to a drastic change in system properties at this hole content that may be connected to various anomalies found in other properties reported in the literature.