Superconductivity in efficient thermoelectric material Cu₃Sb_0.98Al_0.02Se₄

Inspired by the rich physical properties of thermoelectric materials, we have investigated the electrical transport, vibrational, and structural properties of efficient thermoelectric material Cu₃Sb_0.98Al_0.02Se₄ under pressure up to 40.1 GPa. At a critical pressure of 8.5 GPa, a superconducting phase sets in and persists in the pressure range studied. A superconducting dome in the temperature-pressure phase diagram of Cu₃Sb_0.98Al_0.02Se₄ was observed. Meanwhile, pressure-induced structural transition from its initial phase to disorder body-centered cubic structure in Cu₃Sb_0.98Al_0.02Se₄ has been verified by the X-ray diffraction and Raman scattering measurements. Interestingly, the onset of superconductivity coincides with the structural transition, accompanied with the reduction of volume. The superconducting phase was observed in the ultimate formation of the Cu–Sb–Al–Se alloy and was determined to be Im-3m. Based on Hall coefficient measurements, we evaluated the carrier concentration of Cu₃Sb_0.98Al_0.02Se₄, which shows a dramatic increase in the superconducting state. These results suggest that the novel superconductor is realized through the charge transfers and the first-order structural transformation.