Quantized circular photogalvanic effect in chiral Weyl semimetals

Dr. Fernando de Juan Rudolf Peierls Centre for Theoretical Physics

In materials that break inversion symmetry, a light pulse can generate a DC current via what are known as photogalvanic effects. I will start with an introduction arguing that these effects serve as interesting dynamical probe of band structure Berry phases and that they may have larger magnitude than what is commonly thought. I will then describe a surprising topological aspect of the circular photogalvanic effect: in a Weyl semimetal without mirror symmetries, the current it produces is exactly quantized in terms of fundamental constants only. This is because this effect directly measures the monopole charge of a Weyl node, a rare example of quantization in a gapless system at finite frequency. I will discuss potential materials and constraints to observe this effect.

Host: Prof Amalia Coldea

Audrey Wood Seminar Room, Clarendon Laboratory