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arXiv 1107.4957cond-mat.quant-gasphysics.atom-ph
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一维势阱中具有吸引势和任意自旋的费米气体

Fermi gas with attractive potential and arbitrary spin in one-dimensional trap

Pedro Schlottmann, Andrei Zvyagin

摘要:

超冷$^6$ Li原子(有效自旋为1/2)的气体被限制在具有一维性质的细长陷阱中,是显示三种不同相的候选者:(i)束缚在类库珀对状态中的费米子,(ii)未束缚的自旋极化粒子,以及(iii)被认为与FFLO配对有一些相似之处的混合相。将这些研究扩展到具有更高自旋的费米子原子,例如,对于中性$^{40}$ K、$^{43}$ Ca、$^{87}$ Sr或$^{173}$ Yb原子。在巨正则系综中,我们使用一维费米气体与有吸引力的$δ$ -函数势相互作用的精确Bethe {\it反解},研究了基态$S=3/2$的$μ$与$H$相图($μ$是化学势,$H$是外部磁场)。有四种基本状态:粒子可以是不成对的,也可以是两个、三个和四个费米子的束缚态。富相图由这四种状态和各种混合相组成,其中基本状态的组合共存。四个费米子的束缚态在高磁场中是不有利的,但在低磁场中总是存在的。在巨正则系综中工作具有以下优点:(1)通过相对于相互作用强度的缩放获得通用相图;(2)在局域密度近似中探索相分离的可能情况。本文还讨论了塞曼分裂和四极分裂叠加的相图。

英文摘要:

A gas of ultracold $^6$Li atoms (effective spin 1/2) confined to an elongated trap with one-dimensional properties is a candidate to display three different phases: (i) fermions bound in Cooper-pair-like states, (ii) unbound spin-polarized particles, and (iii) a mixed phase which is believed to have some resemblance to the FFLO pairing. It is of great interest to extend these studies to fermionic atoms with higher spin, e.g., for neutral $^{40}$K, $^{43}$Ca, $^{87}$Sr or $^{173}$Yb atoms. Within the grand-canonical ensemble we investigated the $μ$ vs. $H$ phase diagram for $S=3/2$ ($μ$ is the chemical potential and $H$ the external magnetic field) for the ground state using the exact Bethe {\it ansatz} solution of the one-dimensional Fermi gas interacting with an attractive $δ$-function potential. There are four fundamental states: The particles can be either unpaired or clustered in bound states of two, three and four fermions. The rich phase diagram consists of these four states and various mixed phases in which combinations of the fundamental states coexist. Bound states of four fermions are not favorable in high magnetic fields, but always present if the field is low. Working within the grand-canonical ensemble has the following advantages: (1) A universal phase diagram is obtained by scaling with respect to the interaction strength and (2) possible scenarios for phase separation are explored within the local density approximation. The phase diagram for the superposition of a Zeeman and a quadrupolar splitting is also discussed.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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