Exploring the Transition from BCS to Unitarity Using Normal Modes: Energies, Entropies, Critical Temperatures and Excitation Frequencies
Exploring the Transition from BCS to Unitarity Using Normal Modes: Energies, Entropies, Critical Temperatures and Excitation Frequencies
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DOI：
10.1007/s10909-023-02966-2
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发表时间：
2023-05
影响因子：
2
通讯作者：
D. K. Watson
中科院分区：
文献类型：
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作者：
D. K. Watson
对于超冷囚禁的费米气体，采用简正模描述，而不是传统的库珀对，研究了从弱相互作用BCS区到强相互作用么正区的转变。泡利原理是通过使用特定的简正模式赋值而“在纸上”应用的。研究了能量、熵、临界温度和激发频率，并与文献中已有的结果进行了比较。这些简正模是从具有一般两体相互作用的三维哈密顿量的一阶群理论解中解析地推导出来的。在以前的研究中，简正波能够描述获得与基准结果相当的基态能量和热力学量的统一制度，与实验非常吻合。作为这项工作的前奏，研究了从BCS到么正转变的简正模频率行为，并提出了大激发隙和在么正行为的普遍行为的微观基础。目前的研究正在探索这些正常模式频率决定这一转变过程中各种性质的能力，测试这些正常模式的微观动力学产生偏离统一性的可观察行为的能力。结果表明，超流性的物理可以在广泛的粒子间相互作用强度范围内使用简正波来描述，从而为通常用于描述超流性的两体配对模型提供了一个明显的微观替代。
The transition from the weakly interacting BCS regime to the strongly interacting unitary regime is explored for ultracold trapped Fermi gases assuming a normal mode description of the gas instead of the conventional Cooper pairing. The Pauli principle is applied “on paper” using specific normal mode assignments. Energies, entropies, critical temperatures, and an excitation frequency are studied and compared with existing results in the literature. These normal modes have been derived analytically forNidentical, confined particles from a first-ordergroup theoretic solution of a three-dimensional Hamiltonian with a general two-body interaction. In previous studies, normal modes were able to describe the unitary regime obtaining ground-state energies comparable to benchmark results and thermodynamic quantities in excellent agreement with experiment. As a precurser to this work, the behavior of the normal mode frequencies was investigated across the BCS to unitarity transition, and a microscopic basis of the large excitation gaps and universal behavior at unitarity was proposed. The current study now explores the ability of these normal mode frequencies to determine various properties along this transition, testing the ability of the microscopic dynamics of these normal modes to produce observable behavior away from unitarity. The results suggest that the physics of superfluidity can be described using normal modes across a wide range of interparticle interaction strengths and thus offers a clear microscopic alternative to the two-body pairing models commonly used to describe superfluidity along this transition.