超冷费米气体中巡游铁磁转变的理论研究

发布时间：2018-03-10 06:09

本文选题：巡游铁磁转变　切入点：费米气体　出处：《北京科技大学》2017年博士论文　论文类型：学位论文

【摘要】：过渡金属中电子气体的巡游铁磁转变是一种强关联量子现象,其微观机制通常可由Stoner模型予以解释。然而,金属材料中的掺杂和晶格缺陷等因素导致其中的铁磁转变很难在实验中得到灵活调控。随着实验技术的发展,冷原子体系为深入研究巡游铁磁转变提供了新的机遇。本论文采用密度泛函理论,分别对多势阱中费米气体的巡游铁磁转变、有高阶分波存在时费米气体的巡游铁磁转变以及大自旋费米气体中的巡游铁磁转变进行了研究。通过计算体系的基态密度分布,分析和讨论了体系中发生巡游铁磁转变的规律和特点,以期加深对巡游铁磁转变的理解。本文以超冷费米气体为对象,具体研究主要包含如下几个方面：第一,以受限于多势阱中的自旋-1/2费米气体为研究对象,研究了多势阱的几何特征对巡游铁磁转变的影响。结果表明势阱深度的相对大小会显著地影响体系中的巡游铁磁转变。此外,与简谐单阱或双阱相比,多势阱更有利于对实际体系中的磁畴进行观测。第二,以存在高阶分波作用的费米气体为研究对象,研究了不同分波对体系中巡游铁磁转变的影响。一方面,对单独高阶分波的研究结果表明,单独的d-波可以引发巡游铁磁转变,而单独的p-波或f-波均不能引发巡游铁磁转变。另一方面,对s-波和高阶分波共存情况的研究结果表明,d-波与p-波或f-波对于s-波所引发的巡游铁磁转变会产生不同方式的影响。第三,以简谐单阱中的自旋-3/2费米气体为研究对象,研究了不同散射通道对巡游铁磁转变的影响。发现体系中的组分分离通常有两种可能的呈现方式,但只有其中一种对应于巡游铁磁转变。研究还发现当计及自旋混合作用时,上述两种组分分离方式将会受到不同的影响,其中巡游铁磁转变将被加强。
[Abstract]:The transient ferromagnetic transition of electron gases in transition metals is a strongly correlated quantum phenomenon, the microscopic mechanism of which can usually be explained by the Stoner model. However, The doping and lattice defects in metal materials make the ferromagnetic transition difficult to be controlled flexibly in experiments. With the development of experimental technology, The cold atomic system provides a new opportunity for the further study of the cruise ferromagnetic transition. In this paper, the density functional theory is used to study the cruise ferromagnetic transition of Fermi gas in multiple potential wells, respectively. In the presence of high order fractional waves, the ferrite magnetic transition of Fermi gas and the traveling ferromagnetic transition in large spin Fermi gas are studied. The ground state density distribution of the system is calculated. This paper analyses and discusses the rules and characteristics of the ferromagnetic transition in the system, in order to deepen the understanding of the ferromagnetic transition in the cruise. In this paper, the supercooled Fermi gas is taken as the object of study, the specific research mainly includes the following aspects: first, In this paper, the effect of geometrical characteristics of multi-potential well on the ferromagnetic transition of cruising is studied. The results show that the relative magnitude of the depth of the potential well has a significant effect on the cruise ferromagnetic transition in the system, which is confined to the spin -1 / 2 Fermi gas in the multi-potential well, and the effect of the geometric characteristics of the multi-potential well on the ferromagnetic transition in the system is also studied. Compared with simple harmonic single well or double well, multi-potential well is more advantageous to the observation of magnetic domain in practical system. Secondly, the Fermi gas with high-order fractional wave action is taken as the object of study. In this paper, the influence of different partial waves on the ferromagnetic transition in the system is studied. On the one hand, the results of the study on the single high-order wave show that the single d-wave can induce the cruising ferromagnetic transition. On the other hand, neither p- nor f- waves can trigger the ferromagnetic transition of the cruise, on the other hand, The results of the study on the coexistence of S-wave and high-order fractional wave show that the influence of d-wave, p- wave or f- wave on the traveling ferromagnetic transition induced by s- wave will be different. Thirdly, the spin-3 / 2 Fermi gas in a simple harmonic single well is taken as an object of study. The effects of different scattering channels on the ferromagnetic transition in the cruise are studied. It is found that there are usually two possible modes of composition separation in the system, but only one of them corresponds to the ferromagnetic transition. It is also found that when the spin mixing is taken into account, The above two separation methods will be affected by different ways, among which the cruise ferromagnetic transition will be strengthened.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O469

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