PRESSURE-DEPENDENCE OF T-C IN HGBA2CUO4-LESS-THAN-DELTA-LESS-THAN-0.3(DELTA UP TO 18 GPA WITH 0.17)

The superconducting transition temperature T-c of several HgBa2CuO4+de lta samples with 0.17<delta<0.3 has been measured as the function of t he quasi-hydrostatic pressure P up to 18 GPa The observed T-c(max) und er pressure is nearly delta-independent around the optimum doping leve l, demonstrating directly that the pressure-induced charge-transfer on ly plays a minor role in the unusual pressure effects of the Hg-based cuprates. The Grange, over which HgBa2CuO4+delta is superconducting, s ignificantly shrinks under pressure, and the T-c-delta correlation see ms to evolve from parabolic at ambient pressure to truncated-triangle like above 10 GPa