Dependence of the superconducting transition temperature of MgB2 on pressure to 20 GPa

The dependence of T-c on nearly hydrostatic pressure has been measured for an isotopically pure (B-11) MgB2 sample in a helium-loaded diamond-anvil-cell to nearly 20 GPa. T-c decreases monotonically with pressure from 39.1 K at ambient pressure to 20.9 K at 19.2 GPa. The initial dependence is the same as that obtained earlier (dT(c)/dP similar or equal to -1.11(2) K/GPa) on the same sample in a He-gas apparatus to 0.7 GPa. The observed pressure dependence T-c(P) to 20 GPa can be readily described in terms of simple lattice stiffening within standard phonon-mediated BCS superconductivity. (C) 2001 Elsevier Science B.V. All rights reserved.