Devil's Staircase in Semimetals

半金属的恶魔阶梯

基本信息

批准号：
07804020
负责人：
UEDA Kazuo
金额：
$ 1.34万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07804020/
关键词：
Kondo lattice mode semimetal devil's staircas frustration CeSb RKKY interaction Friedel oscillations large Fermi surface デビルズステアケース CeBi CeP

项目摘要

Among the magnetic materials known so far, CeSb has the most complex phase diagram as a function of temperature and magnetic field. The complex magnetic phase diagram is know as the devil's staircase. Generally, the series of CeX (X=P,As, Bi, Sb) have complex magnetic phase diagrams in different degree, which suggeststhat there is a common mechanism for the devil's staircase observed in CeX.A characteristic feature of CeX is smallness of carriers. The carriers of CeX consist of holes at the GAMMA point and electrons at the X points. Under this situation, a new type of scattering processes from holes to electrons and vice versa accompanied by spin exchange with f-spins. This process may be calledoff-diagonal exchange in contrast to the usual exchanges where the scattering are within a band. The momentum transfer associated with his off-diagonal exchange corresponds to the antiferromagnetic wave vector, favoring antiferromagnetic RKKY interaction among the f spins. On the other hand, the ordinary exchanges favor ferromagnetic coupling in the low carrier limit. In this project, we have shown that the frustration between the RKKY interactions originated from these two types of exchange mechanisms is the basic mechanism for the devil's staircase in CeX by using a simple one-dimensional model.Since the origin of the RKKY interaction can be traced back to the Friedel oscillations, we have proceeded to study the spin and charge Friedel oscillations in the Kondo lattice model. By using thedensity matrix renormalization group method, we have observed spin and charge Friedel oscillations. From the period it is concluded that the Fermi volume is large in the sense that the Fermi wavevector isdetermined by the sum of densities of conduction electrons and localized spins.

在迄今为止已知的磁性材料中，CeSb 具有最复杂的温度和磁场函数相图。复杂的磁相图被称为魔鬼的阶梯。一般来说，CeX系列(X=P,As,Bi,Sb)具有不同程度的复杂磁相图，这表明在CeX中观察到的魔鬼阶梯存在共同的机制。CeX的一个特征是载流子小。 CeX 的载流子由 GAMMA 点的空穴和 X 点的电子组成。在这种情况下，一种新型的从空穴到电子的散射过程，反之亦然，并伴随着与 f 自旋的自旋交换。与散射在频带内的通常交换相反，该过程可称为非对角交换。与非对角线交换相关的动量传递对应于反铁磁波矢量，有利于 f 自旋之间的反铁磁 RKKY 相互作用。另一方面，普通交换有利于低载流子极限下的铁磁耦合。在本项目中，我们通过简单的一维模型证明了源自这两类交换机制的 RKKY 交互之间的挫败是 CeX 中魔鬼阶梯的基本机制。由于 RKKY 交互的起源可以追溯到弗里德尔振荡，我们继续研究近藤晶格模型中的自旋和电荷弗里德尔振荡。利用密度矩阵重整化群方法，我们观察到了自旋和电荷弗里德尔振荡。从该周期可以得出结论，费米体积很大，因为费米波矢是由传导电子和局域自旋的密度之和决定的。