Topological phases in the TaSe3 compound

Based on first-principles calculations, we show that stoichiometric TaSe3, synthesized in space group P21/m, belongs to a three-dimensional strong topological insulator (TI) phase with Z2 invariants (1; 100). The calculated surface spectrum shows clearly a single Dirac cone on surfaces, with helical spin texture at a constant-energy contour. To check the stability of the topological phase, strain effects have been systematically investigated, showing that many topological phases survive in a wide range of the strains along both the a and c axes, such as strong TI, weak TI, and Dirac semimetal phases. TaSe3 provides us an ideal platform for experimental study of topological phase transitions. More interestingly, since superconductivity in TaSe3 has been reported for a long time, the coexistence of topological phases and a superconducting phase suggests that TaSe3 is a realistic system to study the interplay between topological and superconducting phases in the future.