Dependence ofTcon hydrostatic pressure in superconductingMgB2

Abstract

The dependence of $T_c$ on hydrostatic (He-gas) pressure for superconducting ${\mathrm{MgB}}_2$ has been determined to 0.7 GPa. We find that $T_c$ decreases linearly and reversibly under pressure at the rate ${\mathrm{dT}}_c/dP\simeq -1.11\pm 0.02\hspace{0.5em}\mathrm{K}/\mathrm{G}\mathrm{P}\mathrm{a}.$ These studies were carried out on the same sample used in earlier structural studies under He-gas pressure which yielded the bulk modulus $B=147.2\mathrm{}\pm 0.7\hspace{0.5em}\mathrm{GPa}.$ The value of the logarithmic volume derivative of $T_c$ is thus accurately determined, $d\ln T_c/d\ln V=+4.16\mathrm{}\pm 0.08,$ allowing quantitative comparison with theory. The present results support the emerging picture that ${\mathrm{MgB}}_2$ is a BCS superconductor with electron-phonon pairing interaction.