Vector optical activity in the Weyl semimetal TaAs

Abstract

It is shown that the Weyl semimetal TaAs can have a significant polar vector contribution to its optical activity. This is quantified by ab initio calculations of the resonant x-ray diffraction at the Ta $L1$ edge. For the Bragg vector (400), this polar vector contribution to the circular intensity differential between left and right polarized x rays is predicted to be comparable to that arising from linear dichroism, which could be tested by future experiments. Implications this result has in regards to optical effects predicted for topological Weyl semimetals are discussed.