Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 21: Solids at Low Temperature - Poster Session

TT 21.7: Poster

Mittwoch, 28. März 2007, 14:00–17:45, Poster A

Mott transition and region of existence of excitonic BEC — •Felix Richter, Rico Schwartz, Tim Schmielau, Klaus Henneberger, and Heinrich Stolz — Institut für Physik, Universität Rostock, 18051 Rostock

We show predictions for the regions of existence of excitons and their BEC in the n,T-plane. Therefor we compute the lowering of the continuum edge as well as shifts in the exciton binding energy due to self-energy shifts. Degeneracy, correlation and exchange are taken into account. Former approaches to this problem yielded a large area of bistability. The exchange shift caused by the bound particles is shown to lead to a significantly smaller area of bistability, which is restricted to densities close to the Mott transistion.

In addition, our algorithm is capable of calculating the density of the condensate. In cuprous oxide, a BEC is predicted to build up at densities lower than that of the Mott transition, making up a considerable amount of the total density.

We compare our results for the binding energy shifts to absorption spectra obtained by pump-probe experiments, which allows for a more precise estimate of the total electron-hole-pair density at any temperature. This provides new insight into the balance between condensation and the Mott transition in an excitonic system.