Dresden 2011 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 85: Poster Session II

HL 85.9: Poster

Donnerstag, 17. März 2011, 18:00–21:00, P4

Numerical Simulation of Exciton Dynamics at Ultra Low Temperature — •Sunipa Som¹ and Heinrich Stolz² — ¹Institut für Physik, Universität Rostock, Rostock, Germany — ²Institut für Physik, Universität Rostock, Rostock, Germany

The possibility of Bose-Einstein condensation of excitons in cuprous oxide has been actively pursued for many years, because in the low density limit excitons are bosons, and therefore obey Bose-Einstein statistics. Cuprous oxide is of high interest due to its long exciton lifetime. We have studied theoretically the relaxation behaviour of excitons at ultra low temperatures below 1K, by solving the Boltzmann equation [1,2], while the excitons are confined within a parabolic potential trap. We have included deformation potential phonon scattering but not collision of excitons.

The Boltzmann equation has been solved by finite difference method and the method of lines using MATLAB. Using initial condition representative for actual experimental studies, we are getting the exciton occupation numbers as a function of momentum, space and time. From these we have calculated the effective temperature and studied how it is changing with time. For temperatures above 1K, the effective temperature is coming down to bath temperature within ten nanoseconds. This is different for temperatures below 1K, where the effective temperature is coming down to bath temperature very slowly within hundreds of nanoseconds only.

[1] Ashcroft and Mermin, Solid State Physics (Harcourt Brace, Fortworth, 1976). [2] A. L. Ivanov et al., Phys. Rev. E 55, 6363 (1997)