RUI - The Physics of Coupled Atomic-Molecular Condensate Systems

该提案的主要目标是探索包含原子和分子物种的多组分冷凝物的物理学，这是物理学研究中发展最快的领域之一。特别令人感兴趣的是双色拉曼光缔合模型（或其Feshbach等价物），也称为非线性系统，其中一对稳定的原子被光缔合（或磁缔合）成不稳定的激发分子，其随后被激光场驱动成稳定的（基态）分子态。非线性系统支持相干布居捕获（CPT）或暗态，这是原子和稳定分子态的叠加。这种CPT态有利于受激拉曼绝热通道（STIRAP），它利用一个违反直觉的脉冲序列将原子相干地转换成稳定的分子，同时避免了与激发态粒子损失相关的退相干。Y. Ling，H. Pu，和B. Putan，Phys. Rev. Lett. 93，250403（2004）]的非线性系统，其中粒子碰撞和陷阱势都不能忽略。绝热条件，它设置了限制的功率和激光脉冲的宽度为一个有效的STIRAP，将研究与CPT状态的集体激发模式。还研究了如何准备系统的问题，通过量子态工程涉及激光，到非线性CPT状态的陷阱电位的存在下，以及如何设计更强大的STIRAP能够有效地转换成分子的原子在相当宽松的CPT条件下的问题。在非线性系统中，创造一个原子凝聚体和一个分子涡旋的相干叠加的可能性也将被研究-这样的叠加代表了一个新的和相对未被探索的物质量子态，独特的耦合原子-分子凝聚体系统。与两个玻色子原子只能在真实的空间中形成紧密束缚的分子不同，两个费米子原子在动量空间中有额外的机会形成束缚的Bardeen-Cooper-Schrieffer（BCS）对。这导致了该建议的最后一个领域，探索耦合费米子原子-分子凝聚体系统的研究有关的BCS原子对的形成和BEC-BCS交叉-从凝聚体的主要绑定BEC分子的BCS对的过渡。

The primary objective of this proposal is to explore the physics of multi-component condensatescontaining both atomic and molecular species, one of the most rapidly evolving areas of physics research. Of particular interest is the two-color Raman photo-association model (or its Feshbach equivalence), also known as the nonlinear system, where a pair of stable atoms is either photo-associated (or magnetoassociated) into an unstable excited molecule, which is subsequently driven into a stable (ground) molecular state by a laser field. The nonlinear system supports a coherent population trapping (CPT) or dark state, which is a superposition of atomic and stable molecular states. Such a CPT state facilitates the stimulated Raman adiabatic passage (STIRAP), which utilizes a counterintuitive pulse sequence to coherently convert atoms into stable molecules while avoiding the decoherence associated with the particle loss in the excited state.The technique of STIRAP will be generalized from recent work [H. Y. Ling, H. Pu, and B.Seaman, Phys. Rev. Lett. 93, 250403 (2004)] to the nonlinear systems, where both particle collisions and trap potentials cannot be ignored. The adiabatic condition, which sets the limit to the powers and the widths of the laser pulses for an efficient STIRAP, will be studied in connection with the collective excitation modes of the CPT state. Also studied is the question of how to prepare the system, through quantum state engineering involving laser light, into the nonlinear CPT state in the presence of trap potentials, and the question of how to design more robust STIRAPs capable of efficiently converting atoms into molecules under quite relaxed CPT conditions. The possibility of creating, in the nonlinear system, a coherent superposition of an atomic condensate and a molecular vortex will also be studied - such a superposition represents a new and relatively unexplored quantum state of matter, unique of the coupled atomic-molecular condensate systems. In contrast to two bosonic atoms, which can only form a molecule tightly bound in real space, two fermionic atoms have the additional opportunity of forming a Bardeen-Cooper-Schrieffer (BCS) pair bound in momentum space. This leads to the final area of the proposal to explore the coupled fermionic atomic-molecular condensate systems for studies related to the formation of BCS atom pairs and to the BEC-BCS crossover - the transition from condensates of mainly bound BECmolecules to that of BCS pairs.