High pressure effects on the superconductivity of beta-pyrochlore oxides AOs2O6

TL;DR

This study investigates how applying high pressure affects the superconducting transition temperatures of beta-pyrochlore oxides AOs2O6 (A = Cs, Rb, K), revealing maximum Tc points and suppression at critical pressures, highlighting the role of electron correlations.

Contribution

It provides new insights into the pressure-dependent superconductivity of beta-pyrochlore oxides and suggests electron correlations and quantum fluctuations are key factors.

Findings

Superconducting Tc increases then peaks under pressure for all compounds.

Superconductivity is suppressed near 6-7 GPa for Rb and K, above 10 GPa for Cs.

Changes in resistivity coefficients correlate with Tc variations.

Abstract

High pressure effects on the superconducting transitions of beta-pyrochlore superconductors AOs2O6 (A = Cs, Rb, K) are studied by measuring resistivity under high pressures up to 10 GPa. The superconducting transition temperature Tc first increases with increasing pressure in all the compounds and then exhibits a broad maximum at 7.6 K (6 GPa), 8.2 K (2 GPa) and 10 K (0.6 GPa) for A = Cs, Rb and K, respectviely. Finally, the superconductivity is suppressed completely at a critical pressure near 7 GPa and 6 GPa for A = Rb and K and probably above 10 GPa for A = Cs. Characteristic changes in the coefficinet A of the T2 term in resistivity and residual resistivity are observed, both of which are synchronized with the corresponding change in Tc. It is suggested that electron correlations and certain quantum fluctuations play important roles in the occurrence or suppression of superconductivity in the beta-pyrochlore oxides.