[seminar] Vivek Pareek, Exciton-exciton interaction in Van der Waals semiconductors

Speaker: Vivek Pareek (Femtosecond Spectroscopy Unit)

Title: Exciton-exciton interaction in Van der Waals semiconductors

Abstract: 

Excitons are bound electron-hole pairs observed in a photo-excited semiconductor system. The fundamental properties of these excitons, such as binding energies, size etc. depend strongly on the dimensionality of the semiconductor. For example, binding energies of excitons is of the order of few milli-electron volts (meV) at room temperature in the traditional 3D semiconductors such as Si or GaAs. However, excitons in the recently discovered two dimensional Van der Waals semiconductors, show binding energy of 100s of meV at room temperature. Similarly, exciton-exciton interaction shows very distinct features for different dimensional semiconductors especially for 1D and 2D semiconductors. In this seminar, I will discuss various aspects of these excitons and their interaction in different semiconductor systems with an emphasis on Van der Waals semiconductors. I will also discuss a particularly interesting case presented by excitons in black phosphorus (BP), where quasi-1D excitons have been observed in atomically thin sheets of BP, resulting in a unique system of 1D excitons in a 2D plane. Using ultrafast spectroscopic techniques, I will tackle the question of the nature of exciton-exciton interaction in bilayer BP.

After the talk, join for discussion with free soft drinks and pizza!