THERMODYNAMICS OF STRAIN-CONFINED PARAEXCITONS IN CU2O
THERMODYNAMICS OF STRAIN-CONFINED PARAEXCITONS IN CU2O
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DOI：
10.1103/physrevb.34.2561
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发表时间：
1986-08-15
影响因子：
3.7
通讯作者：
MYSYROWICZ, A
中科院分区：
文献类型：
--
作者：
TRAUERNICHT, DP;WOLFE, JP;MYSYROWICZ, A
研究了抛物势阱中长寿命准激子的热力学行为。势阱是由赫兹接触应力产生的。波长可调的染料激光器用于直接在势阱中或晶体内的任何其他局部点处产生激子。测量了连续和脉冲激发下激子复合发光的光谱和空间分布。从理论和实验两方面研究了这些长寿命激子的玻色-爱因斯坦凝聚的可能性。我们计算了三维谐振子阱中非相互作用粒子气体发光的光谱和空间分布。直接（无声子）和间接（声子辅助）复合的结果是显着不同的。计算的光谱与在T浴= 2 - 4.2K的中等cw激发的数据进行了比较。单独考虑，无声子光谱表明激子气体处于量子状态;然而，这一结论与气体的估计密度不一致。一个一致的解释所有的光谱和空间分布是可能的，但是，如果一个假设麦克斯韦-玻尔兹曼统计，并考虑到快速变化的仲激子强度与施加的应力。从时间和空间分辨的正激子和准激子发光的研究，在应变阱中的准激子密度的饱和的可能原因推导。首先，碰撞的准激子的俄歇式重组似乎限制了它们的密度，这一想法得到了所观察到的正激子和准激子信号的功率依赖性的支持。其次，观察到应变限制的仲激子的异常缓慢的热化。
The thermodynamic behavior of long-lived paraexcitons confined to a parabolic potential well is examined. The potential well is produced by a Hertzian contact stress. A wavelength-tunable dye laser is used to create excitons directly in the potential well or at any other localized point inside the crystal. Spectral and spatial distributions of the exciton recombination luminescence are measured for cw and pulsed excitation. The possibility of Bose-Einstein condensation of these long-lived excitons is examined both theoretically and experimentally. We calculate the spectral and spatial distribution of luminescence from a gas of noninteracting particles in a three-dimensional harmonic-oscillator well. The results are markedly different for direct (no-phonon) and indirect (phonon-assisted) recombination. The calculated spectra are compared to the data for moderate cw excitation at T bath= 2–4.2 K. Taken alone, the no-phonon spectra suggest that the excitonic gas is in the quantum regime; however, this conclusion is shown to be inconsistent with the estimated density of the gas. A consistent interpretation of all spectral and spatial distributions is possible, however, if one assumes Maxwell-Boltzmann statistics and takes into account the rapidly changing paraexciton intensity with applied stress. From time-and space-resolved studies of the orthoexciton and paraexciton luminescence, plausible causes for a saturation of paraexciton density in the strain well are deduced. First, an Auger-like recombination of colliding paraexcitons seems to limit their density—an idea supported by the observed power dependence of orthoexciton and paraexciton signals. Secondly, an anomalously slow thermalization of strain-confined paraexcitons is observed.