Drumhead Surface States and Topological Nodal-Line Fermions in TlTaSe2

TL;DR

This paper predicts topological nodal-line fermions and associated drumhead surface states in TlTaSe2, revealing unique spin textures and Lifshitz transitions, based on first-principles calculations and effective modeling.

Contribution

It introduces TlTaSe2 as a new topological nodal-line semimetal with protected bulk states and unconventional surface phenomena, distinct from previously known materials.

Findings

Topological nodal-line fermions are predicted in TlTaSe2.

Drumhead surface states exhibit unconventional chiral spin textures.

Lifshitz transition occurs among surface-state pockets.

Abstract

A topological nodal-line semimetal is a new condensed matter state with one-dimensional bulk nodal lines and two-dimensional drumhead surface bands. Based on first-principles calculations and our effective k . p model, we propose the existence of topological nodal-line fermions in the ternary transition- metal chalcogenide TlTaSe2. The noncentrosymmetric structure and strong spin-orbit coupling give rise to spinful nodal-line bulk states which are protected by a mirror reflection symmetry of this compound. This is remarkably distinguished from other proposed nodal-line semimetals such as Cu3NPb(Zn) in which nodal lines exist only in the limit of vanishing spin-orbit coupling. We show that the drumhead surface states in TlTaSe2, which are associated with the topological nodal lines, exhibit an unconventional chiral spin texture and an exotic Lifshitz transition as a consequence of the linkage among multiple drumhead surface-state pockets.