Session 4-2

Abstract

In solid state physics, the notion of geometry and topology for Bloch electrons in solids has provided a new insight into the light-matter interaction in this decade. One such example is the bulk photovoltaic effect called “shift current” that arises from a geometrical (Berry) phase of a Bloch wave function and has a close relationship to the modern theory of electric polarization. While most previous studies of the bulk photovoltaic effects have focused on the photocurrent due to the above band gap excitations of noninteracting electrons, systems of interacting electrons have a potential to support a novel nonlinear functionality. In this talk, I demonstrate that interacting electron systems offer novel photocurrent responses even below the electronic band gap. In particular, I will present a theoretical framework for the photocurrent generation from magnon excitations [1] and its recent experimental observation in multiferroic materials [2].