Drumhead Surface States and Topological Nodal-Line Fermions in TlTaSe2

摘要

A topological nodal-line semimetal is a new condensed matter state withone-dimensional bulk nodal lines and two-dimensional drumhead surface bands.Based on first-principles calculations and our effective k . p model, wepropose the existence of topological nodal-line fermions in the ternarytransition- metal chalcogenide TlTaSe2. The noncentrosymmetric structure andstrong spin-orbit coupling give rise to spinful nodal-line bulk states whichare protected by a mirror reflection symmetry of this compound. This isremarkably distinguished from other proposed nodal-line semimetals such asCu3NPb(Zn) in which nodal lines exist only in the limit of vanishing spin-orbitcoupling. We show that the drumhead surface states in TlTaSe2, which areassociated with the topological nodal lines, exhibit an unconventional chiralspin texture and an exotic Lifshitz transition as a consequence of the linkageamong multiple drumhead surface-state pockets.