Superconducting Transition in the $\beta$-Pyrochlore AOs$_2$O$_6$ (A=Cs, Rb, K) under Pressure

摘要: Pressure dependence of superconducting transition temperature $T_{\rm c}$ has been determined through the DC magnetic measurements under pressure up to $P$=10 GPa for $\beta$-pyrochlore oxides AOs$_2$O$_6$ with A=Cs ($T_{\rm c}$=3.3 K), Rb (6.3 K) and K (9.6 K). Both A=Rb Cs, increases increasing $P$ shows a saturation at cm}$$\sim$8.8 K, which is considered as upper limit inherent in AOs$_2$O$_6$. In contrast, c}-P$ curve KOs$_2$O$_6$ sharp maximum $\sim$10 $P$$\sim$0.5 GPa, higher than cm}$ 0$\leq$$P$$\leq$1.5GPa, suggesting enhanced superconductivity due rattling ions.