Condensed Matter & Surface Sciences

COLLOQUIUM

Michal Grochol

Michigan State University

“Excitons in nanostructures

with perpendicular magnetic field”

The talk consists of two parts:

(i) Exciton diamagnetic shift and disorder. It is shown that the diamagnetic shift varies between different localized exciton states. For describing the disorder in a specific sample, data from cross-sectional scanning tunneling microscopy are used. The potential correlation function deduced from such topographs is taken to generate effective exciton potentials and to simulate the optical properties. Good agreement between measured and simulated values of the diamagnetic shift of individual exciton lines is found.

(ii) Excitons in Nanorings. Excitons are neutral, but composite particles allow us to observe the Aharonov-Bohm effect (a periodic variation with magnetic field of the transition energy). We present calculations of absorption spectra, exciton wave functions, persistent current, and magnetization for different nanostructures. To model the luminescence as well, the relaxation kinetics is studied. For stronger magnetic fields, the ground state becomes optically dark, which results in an increased exciton lifetime.

Thursday, September 18, 2008 -- 4:10 p.m.

Walter Lecture Hall 245