Superconductivity in the geometrically frustrated pyrochlore RbOs2O6 -: art. no. 020503

We report the basic thermodynamic properties of the geometrically frustrated beta-pyrochlore bulk superconductor RbOs2O6 with a critical temperature T-c=6.4 K. Specific heat measurements are performed in magnetic fields up to 12 T. The electronic density of states at the Fermi level in the normal state results in gamma=(33.7+/-0.2)mJ/mol(f.u.)/K-2. In the superconducting state, the specific heat follows conventional BCS-type behavior down to 1 K, i.e., over three orders of magnitude in specific heat data. The upper critical field slope at T-c is 1.2 T/K, corresponding to a Maki-parameter alpha=0.64+/-0.1. From the upper critical field mu(0)H(c2)approximate to6 T at 0 K, we estimate a Ginzburg-Landau coherence length xiapproximate to74 Angstrom. RbOs2O6 is the second reported metallic AB(2)O(6) type pyrochlore compound after KOs2O6, and one of only three pyrochlore superconductors in addition to Cd2Re2O7 and KOs2O6.