Superconductivity in Geometrically Frustrated Pyrochlore RbOs2O6

TL;DR

This paper investigates the thermodynamic properties of the newly discovered geometrically frustrated superconductor RbOs2O6, revealing conventional BCS behavior and key superconducting parameters.

Contribution

It provides the first detailed thermodynamic characterization of RbOs2O6, a new geometrically frustrated pyrochlore superconductor, including critical temperature, specific heat, and critical field measurements.

Findings

Superconducting transition at Tc = 6.4 K.

Specific heat follows BCS behavior down to 1 K.

Upper critical field Hc2 approximately 6 T at 0 K.

Abstract

We report the basic thermodynamic properties of the new geometrically frustrated beta-pyrochlore bulk superconductor RbOs2O6 with a critical temperature Tc = 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 \pm 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 Tc is 1.2 T/K, corresponding to a Maki-parameter alpha = 0.64 \pm 0.1. From the upper critical field mu0 Hc2 \approx 6 T at 0 K, we estimate a Ginzburg-Landau coherence length xi \approx 7.4 nm. RbOs2O6 is the second reported metallic AB2O6 type pyrochlore compound after KOs2O6, and one of only three pyrochlore superconductors in addition to Cd2Re2O7 and KOs2O6.