CdTe微腔中凝聚极化激元的相干特性和发光光谱
Coherence properties and luminescence spectra of condensed polaritons in CdTe microcavities
摘要：
我们分析了二维和有限尺寸的极化激元凝聚体的空间和时间相干特性，其参数适合于最近的实验，这些实验显示了CdTe微腔中的自发和热平衡极化激元凝聚[J.Kasprzak，M. Richard，S. Kunderman，A. Baas，P. Jeambrun，J.M.J. Keeling，F.M. Marchetti，M.H.希曼斯卡河安德烈，J.L. Staehli等人，Nature 443（7110）（2006）409]。我们得到的热长度的理论估计，长度尺度上，充分的相干性有效地存在（超过此幂律衰减的相关性在一个二维的冷凝发生），5微米的顺序。此外，预测的有限尺寸系统的时间相干性的指数衰减与实验中发现的一致。从我们的极化激元凝聚体的发光光谱的分析，考虑到泵浦和衰减，我们得到了一个无色散区在小动量的顺序为4度。此外，我们确定了极化激元线宽作为泵浦功率的函数。最后，我们讨论了如何，通过增加激子光子失谐，它是在原则上可以移动的阈值凝聚从一个区域的相图中的极化激元可以被描述为一个弱相互作用的玻色气体的区域，而不是复合性质的极化激元变得重要。
英文摘要：
We analyse the spatial and temporal coherence properties of a two-dimensional and finite sized polariton condensate with parameters tailored to the recent experiments which have shown spontaneous and thermal equilibrium polariton condensation in a CdTe microcavity [J. Kasprzak, M. Richard, S. Kundermann, A. Baas, P. Jeambrun, J.M.J. Keeling, F.M. Marchetti, M.H. Szymanska, R. Andre, J.L. Staehli, et al., Nature 443 (7110) (2006) 409]. We obtain a theoretical estimate of the thermal length, the lengthscale over which full coherence effectively exists (and beyond which power-law decay of correlations in a two-dimensional condensate occurs), of the order of 5 micrometers. In addition, the exponential decay of temporal coherence predicted for a finite size system is consistent with that found in the experiment. From our analysis of the luminescence spectra of the polariton condensate, taking into account pumping and decay, we obtain a dispersionless region at small momenta of the order of 4 degrees. In addition, we determine the polariton linewidth as a function of the pump power. Finally, we discuss how, by increasing the exciton-photon detuning, it is in principle possible to move the threshold for condensation from a region of the phase diagram where polaritons can be described as a weakly interacting Bose gas to a region where instead the composite nature of polaritons becomes important.
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