Regensburg 2007 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 25: Quantum Liquids, Bose-Einstein Condensates, Ultracold Atoms, ...
TT 25.6: Talk
Thursday, March 29, 2007, 15:15–15:30, H18
Correlation effects and superfluidity in mass-asymmetric electron-hole bilayers — •Alexei Filinov1,2, Patrick Ludwig1, Jens Böning1, Yurii Lozovik2, and Michael Bonitz1 — 1Institute für Theoretische Physik und Astrophysik, Leibnizstrasse 15, 24098 Kiel — 2Institute of Spectroscopy RAS, Troitsk, 142190, Russia
We present an overview on path integral Monte Carlo (PIMC) studies of spatially separated electron-hole bilayers [1]. As was recently observed for bulk semiconductors [2], holes undergo a phase transition to a crystalline state if the mass ratio exceeds Mcr≈ 80. Here, we extend this analysis to bilayers where Mcr depends on d and the in-layer particle density. We consider the low density regime when the spin statistics has a negligible effect on the localized states of the holes. With the decrease of d the crystal melts via the formation of indirect excitons. We also find a crystalline state of excitons at lower temperatures. By considering the excitons as a composite bosons we performed PIMC simulations including the exchange effects. The detailed analysis of dependence of the superfluid fraction in mesoscopic systems (two coupled quantum dots) and macroscopic systems are presented. The role of the finite size effects on the condensate fraction and the critical temperature, and deviation from the macroscopic limit, is discussed.
[1] A.Filinov, P.Ludwig, Yu.E.Lozovik, M.Bonitz and H.Stolz, J. Phys: Conf. Series 35, 197 (2006); Contrib. Plasma Phys., accepted (2007). [2] M.Bonitz, V.S.Filinov, V.E.Fortov. P.R.Levashov, and H.Fehske, J. Phys. A: Math. Gen. 39, 4717 (2006).