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Persistent Currents in Fermionic Quantum Gases

费米子量子气体中的持续电流

基本信息

批准号：
1707557
负责人：
Kevin Wright
金额：
$ 37万
依托单位：
Dartmouth College
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-08-01 至 2022-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1707557&HistoricalAwards=false
关键词：
Persistent Currents Fermionic Quantum Gases

项目摘要

Quantum phenomena are generally most evident at microscopic scales, but there are some special materials where quantum effects are important at large scales. These materials often have extraordinary properties such as superconductivity that make them important for diverse applications such as electrical power distribution, electromagnets, precision sensors, and quantum computing. The many-body quantum physics of these "super" materials can be stunningly complex, and predicting material properties or even the existence of quantum phases of matter has proven to be surprisingly difficult. This award supports laboratory quantum simulation experiments with ultra-cold atoms that will improve our understanding of the mechanisms leading to the formation of superfluid phases, and the way they break down when disturbed in different ways. These experiments will expand present capabilities to create, study, and understand exotic quantum phases of matter that are both of fundamental scientific interest and important to the advancement of technology. In this research program, ultra-cold fermionic atoms (Li-6) will be confined to ring-shaped optical traps, and optical techniques will be used to create persistent currents in the superfluids of fermionic pairs which form when the system temperature is sufficiently low. The initial objective is to create and study persistent currents in a ring-shaped molecular BEC. The researchers will create rotatable Josephson junctions to probe the system and analyze the properties of the system as a function of interaction strength, temperature, and effective dimensionality. These studies will then be extended to include persistent currents in the strongly-interacting unitary limit, and as far into the BCS limit as permitted by the temperatures achievable in the system. The results of these experiments will be analyzed to extract information about the superfluid critical velocity, the transition from phonon-mediated dissipation to pair-breaking excitations, superfluid/condensate fractions, and otherwise validate key theoretical predictions for this important superfluid reference system. Measurements conducted above the superfluid transition temperature will help resolve questions raised by recent experimental observations of persistent currents in mesoscopic normal-metal rings. This program will also establish an essential foundation for longer-term efforts to study the low energy limits of mass and spin transport in unconventional superfluid phases that are less well understood, and/or whose existence has yet to be confirmed.

量子现象通常在微观尺度上最为明显，但在一些特殊材料中，量子效应在大尺度上是重要的。这些材料通常具有非凡的性质，如超导电性，使它们在电力分配、电磁铁、精密传感器和量子计算等各种应用中发挥着重要作用。这些“超级”材料的多体量子物理可能是令人震惊的复杂，预测材料性质，甚至物质的量子相的存在已被证明是出人意料的困难。该奖项支持使用超冷原子进行的实验室量子模拟实验，这些实验将提高我们对导致超流相形成的机制的理解，以及它们在以不同方式受到干扰时的分解方式。这些实验将扩大目前创造、研究和理解物质的奇异量子相的能力，这些相既具有基本的科学意义，也对技术进步具有重要意义。在这个研究计划中，超冷费米子原子(Li-6)将被限制在环形光学陷阱中，并将使用光学技术在系统温度足够低时形成的费米子对超流体中产生持久电流。最初的目标是创建和研究环形分子BEC中的持续电流。研究人员将创建可旋转的约瑟夫森结来探测该系统，并分析该系统的特性作为相互作用强度、温度和有效维度的函数。然后，这些研究将扩展到包括强相互作用单位极限内的持续电流，以及系统中可达到的温度所允许的BCS极限内的持续电流。这些实验的结果将被分析以提取关于超流临界速度、从声子介导的耗散到对破裂激发的转变、超流/凝聚组分的信息，并以其他方式验证这一重要的超流参考系的关键理论预测。在超流体转变温度以上进行的测量将有助于解决最近对介观正常金属环中持续电流的实验观测提出的问题。该计划还将为长期努力研究非常规超流相中质量和自旋输运的低能量极限奠定必要的基础，这些非常规超流相的了解较少，和/或其存在尚未得到证实。