Chiral surface states on the step edge in a Weyl semimetal

Abstract

A Weyl semimetal with a pair of Weyl nodes accommodates chiral states on its flat surface if the Weyl nodes are projected onto two different points in the corresponding surface Brillouin zone. These surface states are collectively referred to as a Fermi arc as they appear to connect the projected Weyl nodes. This statement assumes that translational symmetry is present on the surface and hence electron momentum is a conserved quantity. It is unclear how chiral surface states are modified if the translational symmetry is broken by a particular system structure. Here, focusing on a straight step edge of finite width, we numerically analyze how chiral surface states appear on it. It is shown that the chiral surface states are algebraically (i.e., weakly) localized near the step edge. It is also shown that the appearance of chiral surface states is approximately determined by a simple condition characterized by the number of unit atomic layers constituting the step edge together with the location of the Weyl nodes.