Dynamics of the Formation of Composite Bosons from Fermions

费米子形成复合玻色子的动力学

• 批准号: 0140131
• 负责人: Galina Khitrova
• 金额: $ 41.58万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-04-15 至 2005-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0140131&HistoricalAwards=false
• 关键词: Dynamics; Formation; Composite; Bosons; Fermions

The exciton resonance in semiconductors is often used to demonstrate resonant phenomena first observed with atoms, such as photon echoes, quantum beats, vacuum Rabi splitting, and coherent-field Rabi flopping. Nonresonant optical excitation into the free-carrier continuum produces an entirely different initial condition, much closer to that of a gas plasma whose electrons and ions eventually recombine into atoms that emit photons to return to their ground state. In a semiconductor, the initial plasma consists of free carriers, electrons and holes, whose kinetic energies depend upon how much the excitation energy exceeds the band gap. Exciton formation from the free carriers has been studied for more than four decades, yet little is known. With few exceptions data have been analyzed assuming that each photon emitted with the energy of the 1s electron/heavy-hole transition must have come from an exciton recombining. A recent theoretical breakthrough showed that the plasma emission is also peaked at the 1s resonance. This important finding calls for the reevaluation of all previous conclusions. It is proposed to study the dynamics of exciton formation in a quantum well and to learn how to control the population of the 1s ground state. The goal of the project is to understand the fundamental transition from an initially purely fermionic system (free-carrier plasma generated by optical absorption) to a bosonic system (exciton population). If the bosonic nature of low-density excitons dominates over the fermionic nature of its components, as is the case for atoms, then Bose-Einstein condensation could be achieved in semiconductors at much higher temperatures than those of atomic systems.

半导体中的激子共振通常用于证明首先用原子观察到的共振现象，例如光子回声，量子搏动，真空狂犬分裂和相干场rabi flopping。非共振的光激发对自由载体连续体产生完全不同的初始条件，更接近气体等离子体，其电子和离子最终将光子重新组合到发射光子以返回其基态的原子。在半导体中，初始血浆由游离载体，电子和孔组成，它们的动能取决于激发能量超过频带间隙的程度。从自由载体中研究了四十年来的激子形成，但鲜为人知。除了少数例外，数据被分析了，假设每个带有1s电子/重孔跃迁能量的光子必须来自激子重组。最近的理论突破表明，血浆发射在1S共振处也达到了峰值。这一重要发现要求重新评估所有以前的结论。建议研究量子孔中激子形成的动力学，并学习如何控制1S基态的种群。该项目的目的是了解从最初纯粹的费米子系统（由光吸收产生的自由载体等离子体）到肺泡系统（ICKITON人群）的基本过渡。如果低密度激子的骨气性质在其成分的费尔米金性质上占主导地位，那么与原子的情况一样，在半导体中，在半导体中，在更高的温度下，可以实现Bose-Einstein凝结。