Theory of Ultracold Matter

超冷物质理论

• 批准号: 722-2013
• 负责人: Zaremba, Eugene
• 金额: $ 3.21万
• 依托单位: Queen's University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=568141
• 关键词: Theory; Ultracold; Matter

Broadly speaking, my research deals with dilute atomic gases confined in space and cooled to extremely low temperatures. This combination of conditions results in remarkable physical properties that have captured the attention of physicists around the world. One example of this is the phenomenon of Bose-Einstein condensation (BEC) in which bosonic atoms condense into the lowest available quantum state, the condensate. In this novel state of matter, the atoms act coherently, and exhibit quantum behaviour on scales approaching macroscopic dimensions. One of the more dramatic consequences of BEC is superfluidity: the possibility of flow without resistance or dissipation. Superfluidity underlies much of the research described in this proposal. Perhaps the simplest example is the undamped oscillatory motion of a condensate at zero temperature. However, at elevated temperatures, the oscillations are damped as a result of the interaction of the condensate with the thermal excitations, the so-called thermal cloud. The theory we have developed accounts for this behaviour. Similar dissipative effects are also observed when considering the dynamics of a vortex - the quantized circulation of atoms around a central core. If such a vortex were to be created in a trapped Bose gas, it would spiral out towards the edge of the gas as a result of its interaction with the thermal cloud, and would eventually disappear. This too is described by the theory we have developed. One of the fascinating aspects of cold atoms is that they can be manipulated in various ways. For example, if a standing light wave is imposed, the atoms effectively find themselves in a periodic potential which we call an optical lattice. Here, too, superfluidity exists. However, if the optical lattice is deepened, the atoms make a transition to an insulating state, a completely different quantum phase. One direction of my research concerns the quantum phase transitions that occur when a mixture of bosonic atoms resides in the lattice. The ultimate objective of all this work is to enhance our ability to further control and manipulate cold trapped atoms.

广义地说，我的研究涉及被限制在太空中并被冷却到极低温度的稀释原子气体。这种条件的组合导致了引人注目的物理特性，引起了世界各地物理学家的注意。其中一个例子是玻色-爱因斯坦凝聚（BEC）现象，其中玻色子原子凝聚成最低的可用量子态，即凝聚态。在这种新的物质状态下，原子的行为是一致的，并在接近宏观尺度的尺度上表现出量子行为。BEC的一个更引人注目的结果是超流性：没有阻力或耗散的流动的可能性。 超流性是本提案中所描述的许多研究的基础。也许最简单的例子是零温度下凝聚态的无阻尼振荡运动。然而，在升高的温度下，由于冷凝物与热激发的相互作用，即所谓的热云，振荡被阻尼。我们发展的理论解释了这种行为。当考虑涡旋的动力学时，也观察到类似的耗散效应-原子围绕中心核的量子化循环。如果这样一个漩涡是在一个被困玻色气体中产生的，它将由于与热云的相互作用而朝着气体的边缘螺旋出去，并最终消失。这也是我们发展的理论所描述的。 冷原子的迷人之处之一是它们可以以各种方式被操纵。例如，如果施加一个驻波，原子实际上会发现自己处于一个周期性的势中，我们称之为光学晶格。这里也存在超流性。然而，如果光学晶格加深，原子就会过渡到绝缘状态，这是一个完全不同的量子相位。我的研究方向之一是当玻色子原子的混合物存在于晶格中时发生的量子相变。所有这些工作的最终目标是提高我们进一步控制和操纵冷原子的能力。