Ta2NiSe5: a candidate topological excitonic insulator with multiple band inversions

TL;DR

This paper investigates the complex topological electronic structures of Ta2NiSe5, revealing multiple band inversions and Dirac surface states, positioning it as a promising 3D topological excitonic insulator.

Contribution

It demonstrates that Ta2NiSe5 exhibits multiple parity and band inversions, making it a novel candidate for a topological excitonic insulator with complex topological features.

Findings

Multiple parity and band inversions in Ta2NiSe5.

Presence of Dirac cone surface states.

Complex topologically nontrivial electronic structures.

Abstract

The electronic structures and topological properties of the orthorhombic and monoclinic phases of the quasi-one-dimensional excitonic insulator Ta2NiSe5 are investigated based on density functional theory. In contrast to a single parity or band inversion across the Fermi level in many topological insulators studied previously, there are multiple parity and band inversions with or without spin-orbit coupling in both phases of Ta2NiSe5, resulting in more complex and topologically nontrivial electronic structures. The Dirac cone type surface states of the low-temperature monoclinic phase are also obtained. In this paper, we demonstrate that Ta2NiSe5 is a promising candidate as a three-dimensional topological excitonic insulator.