Observation of the Transition from Semiconductor to High-$T_c$ Superconductor in ${\left({\mathrm{Sn}}_x{\mathrm{Eu}}_{1-x}\right)}_y{\mathrm{Mo}}_6{\mathrm{S}}_8$ under High Pressure

Pressure-induced high-temperature superconductivity is observed in semiconducting ${\left({\mathrm{Sn}}_x{\mathrm{Eu}}_{1-x}\right)}_y{\mathrm{Mo}}_6{\mathrm{S}}_8$, where $0<~x<~0.1$ and $y=1.0\mathrm{} \mathrm{and} 1.2$, having a carrier concentration ≃${10}^{19}$/${\mathrm{cm}}^3$ at 4.2 K as determined from Hall-effect measurements. Above a threshold pressure ≃7 kbar, superconductivity appears with $\frac{d{T}_c}{\mathrm{dP}}\simeq 2$ K/kbar. The maximum superconducting temperature ($T_c\sim 10$ K), reached at ∼ 12 kbar, represents the highest pressure-induced $T_c$ in any semiconductor. For $P>~13$ kbar, the temperature-dependent resistance appears metallic.