Many-body effects on properties of attractive Bose-Einstein condensates.

从多体效应和吸引相互作用两个方面研究了相互作用对气态玻色-爱因斯坦凝聚物性质的影响。以下是我们主要结果的总结。(1)快速旋转BEC。我们已经证明，当系统的角动量超过h N（N-1）时，旋转BEC会发生量子相变到劳克林态，其中N是原子数。在劳克林态之上，我们发现了一个类似于转动分支的单粒子激发分支。这一分支已在具有长程库仑相互作用的分数量子霍尔系统中被发现。我们的系统具有短距离，因此提供了对这种间隙模式的新见解。BEC通常在限定电位中产生。众所周知，在高于一维的维度中，BEC在自由空间中要么坍缩，要么膨胀。我们已经证明，利用费什巴赫共振振荡吸引相互作用和排斥相互作用之间的相互作用强度，可以在二维自由空间中稳定BEC。(3)在三维自由空间中，我们发现上述方法不能稳定BEC，但在存在耗散的情况下可以稳定BEC。物质的这种状态可以看作是自由空间中自困的气态超流体。

We have studied effects of interactions on properties of gaseous Bose-Einstein condensates (BECs) by focusing on many-body effect and attractive interactions. Below follows the summary of our main results.(1) Fast rotating BEC. We have shown that a rotating BEC makes a quantum phase transition to the Laughlin state when the angular momentum of the system exceeds h N(N-1), where N is the number of atoms. Above the Laughlin state we find a single-particle excitation branch similar to the roton branch. This branch has been found in fractional quantum Hall systems with a long-range Coulomb interaction. Our system has short-ranged and therefore offers a new insight into this gapful mode.(2) A BEC is usually created in a confining potential. It is well known that in dimensions higher than one dimension BEC will either collapse or expand in free space. We have shown that the BEC can be stabilized in 2D free space by oscillating the strength of interactions between attractive and repulsive interactions using a Feshbach resonance.(3) In 3D free space, we have found that BEC cannot be stabilized by the above method, but can be stabilized in the presence of dissipation. This state of matter may be viewed as a self-trapped gaseous superfluid in free space.