High pressure structural and magneto-transport studies on type-II Dirac semimetal candidate Ir2In8S: Emergence of superconductivity upon decompression

The structural and magneto-transport properties of type-II Dirac semimetal candidate Ir2In8S have been investigated under high pressure. The ambient tetragonal structure (P4_2/mnm) is found to be stable up to 7 GPa, above which the system takes an orthorhombic Pnnm structure, possibly destroying the Dirac cones due to the loss of the four-fold screw symmetry. In the tetragonal structure, a gradual suppression of the transverse magneto-resistance and a rapid change in the magnetic field dependence above 50K suggest possible T-dependent Fermi surface modification. In the high pressure phase, the metallic character increases marginally (as evident from the increased RRR value) accompanied with suppressed magneto-resistance, without emergence of superconductivity up to 20 GPa and down to 1.4K. Most surprisingly, upon release of pressure to 0.2 GPa, a sharp resistance drop below 4K is observed, field varying measurements confirm this as the onset of superconductivity. The observed changes of the carrier density and mobility in the pressure-released tetragonal phase indicate electronic structural modification resulting from the irreversible polyhedral distortion. A simultaneous increase in the residual resistivity and carrier density upon decompression indicates that an enhanced impurity scattering play a key role in the emergence of superconductivity in the tetragonal Ir2In8S, making it an ideal platform to study topological superconductivity.