Online

September 18(Fri.), 2020 / 14:00 - 15:00(KST)

We introduce the notion of combinato. The responses of materials to strong electric fields, i.e., nonlinear optical responses and nonlinear trnsport, constitute a vast field of physics and engineering. While geometry and topology has been playing a central role in recent studies of condensed matter, geometrical aspects of nonlinear responses have not been fully explored so far. In this talk, I will show a few exmple of geometrical nonlinear responses. First, I will explain that the second-order nonlinear optical effect, the shift-current, has a close relationship to the modern theory of polarization, and is described by the Berry connection of Bloch wave function. I present how electron correlations can enhance/modify shift current response inversion broken materials such as magnets. Next, I show that nonlinear transport in tunneling problems (Landau-Zener tunneling) leads to direction-dependent current response, i.e., nonreciprocal current, which is also governed by Berry phase.

Prof. Takahiro Morimoto (The University of Tokyo)

1) Please join with your email (no guest acc't) and write your full name & affiliation

    - E.g. Name: Full name(affiliation)

2) Join with the following link 

1) Type "APCTP" in the YouTube Search bar

2) Click the video with 'live now' sign

Gil Young Cho (POSTECH)