Pressure Effects on T_c of Superconductor YBa₂Cu₄O₈

Abstract

The enhancement of the superconducting transition temperature by pressure was studied up to 2 GPa for an YBa 2 Cu 4 O 8 compound which was synthesized by using the canned HIP technique. The value of d T c /d P was found to be 5.5 K/GPa. From the experiments of the specimen in which YBa 2 Cu 4 O 8 and Y 2 Ba 4 Cu 7 O 14 compounds coexist, d T c /d P for Y 2 Ba 4 Cu 7 O 14 was also shown to be 5.5 K/GPa. The result for the YBa 2 Cu 4 O 8 compound is explained by the pressure induced carrier (hole) redistribution on the basis of the calculation of the Madelung energy.