Superconductivity and Rattling under High Pressure in the \beta-Pyrochlore Oxide RbOs2O6

概要

論文の詳細を見る
Rattling-induced superconductivity in the \beta-pyrochlore oxide RbOs2O6 is investigated under high pressures up to 6 GPa. Resistivity measurements in a high-quality single crystal show that the superconducting transition temperature T_{\text{c}} increases gradually from 6.3 K at ambient pressure to 8.8 K at 3.5 GPa, surprisingly remains almost constant at 8.8\pm 0.1 K in a wide pressure range between 3.5 (P_{\text{o}}) and 4.8 GPa, and suddenly drops to 6.3 K at P_{\text{s}} = 4.9 GPa, followed by a gradual decrease with further pressure increase. Two anomalies in the temperature dependence of the normal-state resistivity are observed at P_{\text{o}}< P < P_{\text{s}} and P > P_{\text{s}}, revealing the presence of two high-pressure phases corresponding to the changes in T_{\text{c}}. The rattling of the Rb ion inside a cage made of Os and O atoms may be slightly and seriously modified in these high-pressure phases that probably have cages of reduced symmetry, respectively, so that electron--rattler interactions that govern the superconducting and transport properties of \beta-RbOs2O6 are significantly affected.
2011-10-15