Pressure tuning of superconductivity in Mo8Ga41 single crystals

Abstract

We report on pressure tuning of superconductivity in a strongly coupled superconductor ${\mathrm{Mo}}_{8}{\mathrm{Ga}}_{41}$ with a critical temperature ${T}_{c}\ensuremath{\sim}9.8\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Resistance measurements show that ${T}_{c}$ is suppressed to 3.6 K at 19 GPa followed by a nonmonotonic variation at higher pressures. Synchrotron x-ray diffraction experiments reveal an amorphization taking place at the critical pressure ${P}_{c}\ensuremath{\sim}19\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$. As comparing with $\mathrm{Mg}{\mathrm{B}}_{2}$, the ${\mathrm{Mo}}_{8}{\mathrm{Ga}}_{41}$ shows a relative low decreasing rate of ${T}_{c}$, which might be attributed to its unique vertex-sharing type of cluster architecture. Survival of superconductivity across the crystalline to amorphous transition indicates that, although long-range structural order of endohedral Ga clusters is destroyed, short-range-ordered intracluster structure still exists and allows for local Cooper pairing. Due to presence of disorders in the amorphous phase, establishment of Cooper pair coherence is shifted to lower temperatures, which causes unusual transport behaviors near ${T}_{c}$, e.g., the anomalous resistance peak and dip. The amorphous superconducting phase is able to be retained to ambient pressure and therefore provides an ideal platform to study disorder effects on superconductivity.