Superconductivity at 20 K in yttrium metal at pressures exceeding 1 Mbar

In experiments in a diamond anvil cell, yttrium metal is found to display a superconducting transition temperature in the ac susceptibility which increases monotonically from 3.5 K at 30 GPa to 19.5 K at 115 GPa, where the transition onset lies at 20 K. This is the second highest value of T-c ever observed for an elemental superconductor. A fit to the Y data using the McMillan equation is consistent with electron-phonon superconductivity with moderately strong coupling. (c) 2006 Elsevier B.V. All rights reserved.