Discovery of Superconductivity in Mercury Cadmium Telluride

Mercury cadmium telluride compounds exhibit large tunability of nontrivial electronic states by modifying chemical composition, temperature, or pressure. Despite the growing interest in Hg_1-xCd_xTe, very little information currently exists on how their electrical properties are affected upon compression. Here, we systematically investigate the high-pressure behaviors of bulk Au-doped Hg_0.781Cd_0.219Te crystals with the doping level close to the Kane fermion point. A clear structure evolution path of this compound with pressure varying from zinc blende (F43̅m) through cinnabar (P3₁21) and rocksalt (Fm3̅m) to the orthorhombic one (Cmcm) is established from the measurements of phonon spectra, resistivity, and the Hall effect. Pressure-induced phonon softening is proposed to be the driving force for the phase transition. The last two phases are found to exhibit superconductivity with different pressure dependence of the critical temperature. These results and findings suggest that superconductivity is the general nature of mercury cadmium tellurium compounds at high pressures. The group II-VI compounds thus also offer a pool for finding new superconductors.