Bulk Fermi surface of the layered superconductor TaSe3 with three-dimensional strong topological insulator state

TL;DR

This study combines high magnetic field transport measurements and ab initio calculations to reveal that TaSe3 is a three-dimensional strong topological insulator with complex Fermi surface features, making it a promising platform for topological superconductivity.

Contribution

The paper provides the first combined experimental and theoretical evidence that TaSe3 hosts a strong topological insulator state with specific Fermi surface characteristics and a Dirac cone on its surface.

Findings

Identification of nontrivial electron and hole Fermi pockets at B and Γ points.

Observation of anisotropic Fermi surface features through angle-dependent quantum oscillations.

Confirmation of a single Dirac cone with helical spin texture on the surface.

Abstract

High magnetic field transport measurements and ab initio calculations on the layered superconductor TaSe3 have provided compelling evidences for the existence of a three-dimensional strong topological insulator state. Longitudinal magnetotransport measurements up to ~ 33 T unveiled striking Shubnikov-de Hass oscillations with two fundamental frequencies at 100 T and 175 T corresponding to a nontrivial electron Fermi pocket at the B point and a nontrivial hole Fermi pocket at the {\Gamma} point respectively in the Brillouin zone. However, calculations revealed one more electron pocket at the B point, which was not detected by the magnetotransport measurements, presumably due to the limited carrier momentum relaxation time. Angle dependent quantum oscillations by rotating the sample with respect to the magnetic field revealed clear changes in the two fundamental frequencies, indicating anisotropic electronic Fermi pockets. The ab initio calculations gave the topological Z2 invariants of (1; 100) and revealed a single Dirac cone on the (1 0 -1) surface at the X point with helical spin texture at a constant-energy contour, suggesting a strong topological insulator state. The results demonstrate TaSe3 an excellent platform to study the interplay between topological phase and superconductivity and a promising system for the exploration of topological superconductivity.