Pressure effects on Tc in superconducting (Tl, Cs)1-xFe2-ySe2.

Hydrostatic-pressure (up to 0.96 GPa) dependence of Tc in a newly discovered Fe-based superconductor (Tl0.59Cs0.26)Fe1.9Se2 (Tc = 28 K, at ambient pressure) is reported. Static magnetization measurements under pressure indicate that the linear increase in Tc is initially rapid (dTc/dP ∼ 9.9 K · GPa-1) but slows down to dTc/dP ∼ 2.5 K · GPa-1 for P ≧ 0.18 GPa. The Tc of the superconducting phase is 32 K at pressure P = 0.96 GPa. The simple rigid band model or the Bardeen, Cooper, Schrieffer theory may not be sufficient to account for our observations, if one assumes that the lattice parameters would be linearly decreased with pressure. [ABSTRACT FROM AUTHOR]