标题： 三层半导体量子霍尔铁磁体的赝自旋各向异性 显示英文标题

标题： Pseudospin anisotropy of trilayer semiconductor quantum Hall ferromagnets

摘要： 当两个朗道能级在整数量子霍尔效应区域中与化学势接近重合时，这两个朗道能级可以刚好交叉或坍缩，而引起对齐的外部或赝自旋场则发生变化。 在本工作中，所有可能的交叉情况都通过变分哈特里-福克近似理论分析了半导体三层系统的特殊情况。 该模型包括相邻层之间的隧穿、偏压、层内和层间电子库仑相互作用。 我们发现，在双层系统中使用的普遍赝自旋各向异性分类方案也适用于三层情况，其中简单的交叉对应于易轴铁磁各向异性类比，而坍缩情况对应于易面铁磁各向异性类比。 一种各向同性的情况也是可能的，根据填充因子以及两个邻近能级的量子数，能级可以刚好交叉或坍缩。 虽然我们的结果适用于任何整数填充因子$\nu$ (=1,2,3,...)，但我们详细分析了在$\nu=3$和$4$的交叉情况，并给出了明确的预测，这将有助于它们的实验搜索。 特别是，目前的计算表明，通过增加偏压，可以在这些两个填充因子下将三层层系统从易面各向异性区域驱动到易轴区域，然后再驱动回易面区域。 这种再进入行为是三层层系统相对于双层系统的一个独特特征。 显示英文摘要

摘要： When two Landau levels are brought to a close coincidence between them and with the chemical potential in the Integer Quantum Hall regime, the two Landau levels can just cross or collapse while the external or pseudospin field that induces the alignment changes. In this work, all possible crossings are analyzed theoretically for the particular case of semiconductor trilayer systems, using a variational Hartree-Fock approximation. The model includes tunneling between neighboring layers, bias, intra-layer and inter-layer Coulomb interaction among the electrons. We have found that the general pseudospin anisotropy classification scheme used in bilayers applies also to the trilayer situation, with the simple crossing corresponding to an easy-axis ferromagnetic anisotropy analogy, and the collapse case corresponding to an easy-plane ferromagnetic analogy. An isotropic case is also possible, with the levels just crossing or collapsing depending on the filling factor and the quantum numbers of the two nearby levels. While our results are valid for any integer filling factor $\nu$ (=1,2,3,...), we have analyzed in detail the crossings at $\nu=3$ and $4$, and we have given clear predictions that will help in their experimental search. In particular, the present calculations suggest that by increasing the bias, the trilayer system at these two filling factors can be driven from an easy-plane anisotropy regime to an easy-axis regime, and then can be driven back to the easy-plane regime. This kind of reentrant behavior is an unique feature of the trilayers, compared with the bilayers.