RUI - The Physics of Coupled Atomic-Molecular Condensate Systems

这一提议的主要目标是探索同时包含原子和分子物种的多组分凝聚的物理学，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(或其费什巴赫等价)，也被称为非线性系统，其中一对稳定的原子要么光缔合(或磁缔合)成不稳定的激发分子，后者随后被激光场驱动到稳定的(基态)分子状态。该非线性系统支持相干布居俘获(CPT)或暗态，这是原子态和稳定分子态的叠加。这种受激拉曼绝热通道(STIRAP)利用反直觉的脉冲序列来相干地将原子转化为稳定的分子，同时避免了与激发态中的粒子损失相关的退相干。莱特牧师。93,250403(2004年)]到非线性系统，其中粒子碰撞和囚禁势都不能被忽略。绝热条件为有效的STIRAP设置了激光脉冲的功率和宽度的极限，我们将结合CPT态的集体激发模式来研究它。还研究了如何通过涉及激光的量子态工程将系统制备成存在陷阱势的非线性CPT态，以及如何设计更健壮的STIRAP，能够在相当宽松的CPT条件下有效地将原子转化为分子。还将研究在非线性系统中创建原子凝聚体和分子涡旋的相干叠加的可能性-这种叠加代表了一种新的、相对未被探索的物质量子状态，这是耦合的原子-分子凝聚系统所独有的。两个玻色子原子只能在实空间中形成紧密束缚的分子，而两个费米子原子有额外的机会形成束缚在动量空间中的Bardeen-Cooper-Schrieffer(BCS)对。这导致了为研究BCS原子对的形成和BEC-BCS交叉-从主要结合的BEC分子的凝聚体到BCS对的凝聚体的研究而探索耦合的费米子原子-分子凝聚体系的最后领域。

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.