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arXiv 1702.02041cond-mat.mes-hallcond-mat.str-el
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Bernevig-Hughes-Zhang模型中二维电子的两体问题

Two-body problem for two-dimensional electrons in Bernervig-Hughes-Zhang model

Vladimir A. Sablikov

AI总结:

本研究针对对称化Bernevig-Hughes-Zhang模型下的二维电子两体问题,发现相互作用电子可形成带隙内束缚态,且拓扑相中的能带反转可在低作用势下催生高结合能的新束缚态。

摘要:

我们研究了对称化Bernevig-Hughes-Zhang(贝内维格-休斯-张)模型下二维电子系统的两体问题,该模型被广泛用于描述拓扑绝缘体与常规绝缘体。核心研究结果是,两个存在相互作用的电子可以形成束缚态,其能量处于能带谱的能隙之中。这种配对机制可被解释为两个电子形成了负约化有效质量。由于电子的相对运动与质心运动相互耦合,该问题较为复杂。我们考虑总动量为零的情况,针对阶梯形式的排斥相互作用势开展了详细计算。我们根据自旋结构以及构成给定束缚态的双粒子基函数对这些态进行了分类。我们分析了拓扑相和平庸相两种情形下束缚态的能谱与电子结构,重点关注了能带反转以及电子-空穴带耦合带来的效应。在平庸相,以及耦合参数$a$较大的拓扑相中,束缚态能谱在定性上是相似的。但当$a$小于某一特定值时,情况会发生剧烈变化。在拓扑相中,更低的相互作用势下会出现结合能更高的新态,这证明能带反转能够促进电子配对。

英文摘要:

We study the two-body problem for two-dimensional electron systems in a symmetrized Bernevig-Hughes-Zhang model which is widely used to describe topological and conventional insulators. The main result is that two interacting electrons can form bound states with the energy in the gap of the band spectrum. The pairing mechanism can be interpreted as the formation of a negative reduced effective mass of two electrons. The problem is complicated because the relative motion of the electrons is coupled to the center-of-mass motion. We consider the case of zero total momentum. Detail calculations are carried out for the repulsive interaction potential of steplike form. The states are classified according to their spin structure and two-particle basis functions that form a given bound state. We analyze the spectra and electronic structure of the bound states in the case of both topological and trivial phases and especially focus on effects originating from the band inversion and the coupling of the electron and hole bands. In the trivial phase and the topological phase with the large coupling parameter $a$, the bound state spectra are qualitatively similar. However, when $a$ is less a certain value, the situation changes dramatically. In the topological phase, new states arise with a higher binding energy at lower interaction potential, which evidences that the band inversion can favor pairing the electrons.

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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