Topological Phases in Quasi One Dimensional Material TaSe₃ under Pressure

TaSe₃ is a quasi 1D material, which is a superconductor at very low temperatures and was recently characterized as a Topological Insulator (TI). The existence of non-trivial topology in an intrinsically superconducting material might make the realisation of Majorana Fermions possible, thus advancing the efforts in the field of quantum computing. We aim to understand the effect of hydrostatic pressure on the electronic and structural properties of TaSe₃, using first principles calculations combined with Raman spectroscopy. Our calculations reveal that TaSe₃ undergoes two topological phase transitions under the application of pressure, around 5 GPa and 7 GPa. The first transition occurs from a weak topological insulator phase to a strong TI phase, while the second transition, around 7GPa, is from a strong to weak topological insulator phase. The weak TI hosts an even number of Dirac cones, which annihilate in the presence of strong disorder, while the strong TI phase hosts an odd number of Dirac cones on all its surfaces, which are protected against disorder by Time Reversal Symmetry. The Dirac cone in the strong insulating phase and the corresponding Fermi arc are also plotted, which shows the linear dispersion of the Dirac fermions. Our study provides a careful analysis of the topological nature of TaSe₃ at ambient pressure and reveals the role of hydrostatic pressure in tuning the electronic bands and the surface spectrum of a Topological Insulator.