Spontaneous charge current in a doped Weyl semimetal

A Weyl semimetal hosts low-energy chiral surface states, which appear to connect a pair of Weyl nodes in reciprocal space. As these chiral surface states propagate in a given direction, a spontaneous circulating current is expected to appear near the surface of a singly connected Weyl semimetal. This possibility is examined by using a simple model with particle–hole symmetry. It is shown that no spontaneous charge current appears when the Fermi level is located at the band center. However, once the Fermi level deviates from the band center, a spontaneous charge current appears to circulate around the surface of the system and its direction of flow is opposite for the cases of electron doping and hole doping. These features are qualitatively unchanged even in the absence of particle–hole symmetry. The circulating charge current is shown to be robust against weak disorder. (author)