Condensed Matter Seminar: The force that couples electrons and excitons

Christian Fey (MPQ)
Excitons are quasiparticles formed by an electron-hole pair that behave similar to hydrogen atoms but possess a different mass and binding energy.

Christian Fey (MPQ)
Online Seminar
Mon 04. May 2020, 11:30 am (MEZ)

Abstract:

Excitons are quasiparticles formed by an electron-hole pair that behave similar to hydrogen atoms but possess a different mass and binding energy. Exceptionally strongly bound excitons can be found in atomically thin layers of semiconductors that are made of transition metal dichalcogenides (TMD). Such robust excitons promise fascinating future applications such as exciton-mediated superconductors or semiconductor-based quantum simulators. However, for the realization of these prospects a detailed understanding of the underlying interactions is crucial. To this end we develop an exact diagonalization approach that simulates the physics of three interacting charges in monolayer TMD and allows us to derive the force between excitons and electrons [1]. Additionally, we obtain properties of bound states, so called trions, as well as exotic excited states composed of a rotating exciton and a counter-rotating electron. As an application we use the derived interaction model to predict the photoabsorption properties of electron-doped TMD, which reveals the existence of exciton-polarons -- excitons dressed by a coat of electronic excitations.

[1] C. Fey, P. Schmelcher, A. Imamoglu, R. Schmidt, arxiv 1912.04873 ; accepted in PRB (2020)