Optical evidence of the chiral magnetic anomaly in the Weyl semimetal TaAs
Antonio L. Levy, Andrei Sushkov, Fengguang Liu, Bing Shen, Ni Ni, Howard D. Drew, Gregory Jenkins
Chiral pumping from optical electric fields oscillating at THz frequencies is observed in the Weyl material TaAs with electric and magnetic fields aligned along both the a- and c-axes. Free carrier spectral weight enhancement is measured directly for the first time, confirming theoretical expectations of chiral pumping. A departure from linear field-dependence of the Drude weight is observed at the highest fields in the quantum limit, providing evidence of field-dependent Fermi velocity of the chiral Landau level. Implications for the chiral magnetic effect in Weyl semimetals from the optical f-sum rule are discussed.