Expansive Open Fermi Arcs and Connectivity Changes Induced by Infrared Phonons in ZrTe₅

Expansive open Fermi arcs covering most of the surface Brillouin zone (SBZ) are desirable for detection and control of many topological phenomena, but so far has been only reported for Kramers-Weyl points, pinned at time-reversal invariant momentum in chiral materials. Here from first-principles calculations, the conventional Weyl points in ZrTe₅ with the chirality of +1/–1 near the BZ center at general momentum are shown to also form expansive open Fermi arcs across the SBZ boundary to occupy most of the SBZ, which is induced by one of the infrared phonons, the second lowest B_1u mode for breaking inversion symmetry. Such expansive open Fermi arcs are revealed to evolve from the topological surface states that connect multiple surface Dirac points on the (001) surface of the topological insulator phase without lattice distortion in ZrTe₅. Furthermore, the connectivity of the induced open Fermi arcs can be changed by the magnitude of the lattice distortion of this infrared phonon mode. Thus, coherent optical phonon can be used to modulate lattice distortion to induce novel topological features including expansive open Fermi arcs and also dynamically control Fermi arcs connectivity in ZrTe₅.