Optical investigations of pressure-induced phases in type-II Weyl semi-metal WTe₂

WTe₂ crystalizes in the T_d structure at an ambient pressure, and undergoes a structural phase transition to the 1T’ structure under the application of pressure. We investigated pressure-induced variation of structural and electronic phases by optical methods. Whereas we observed several clear signatures of pressure-induced phase transitions consistently with previous reports, we could characterize the intermediate state existing between two structural phases of T_d and 1T’, which would be related to the pressured-induced superconductivity observed in WTe₂.