Colossal Bulk Photovoltaic Effect in a Weyl Semimetal*

The bulk photovoltaic effect (BPVE) is a second-order non-linear optical effect which directly converts light into an electrical current. This effect is intimately related to the topological nature of the material, and is in fact directly proportional to the Berry connection. We present photocurrent measurements on the Weyl semimetal TaAs, where the diverging Berry connection leads to the largest observed BPVE, as well as the first observation of BPVE utilizing mid-infrared radiation.