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首页> 外文期刊>Physical review >Topological phase transitions in (Bi_(1-x)In_x)_2Se_3 and (Bi_(1-x)Sb_x)_2Se_3
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Topological phase transitions in (Bi_(1-x)In_x)_2Se_3 and (Bi_(1-x)Sb_x)_2Se_3

机译：（Bi_（1-x）In_x）_2Se_3和（Bi_（1-x）Sb_x）_2Se_3中的拓扑相变

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We study the phase transition from a topological to a normal insulator with concentration x in (Bi_(1-x)In_x)_2Se_3 and (Bi_(1-x)Sb_x)_2Se_3 in the Bi_2Se_3 crystal structure. We carry out first-principles calculations on small supercells, using this information to build Wannierized effective Hamiltonians for a more realistic treatment of disorder. Despite the fact that the spin-orbit coupling (SOC) strength is similar in In and Sb, we find that the critical concentration x_c is much smaller in (Bi_(1-x)In_x)_2Se_3 than in (Bi_(1-x)Sb_x)_2Se_3 For example, the direct supercell calculations suggest that x_c is below 12.5% and above 87.5% for the two alloys, respectively. More accurate results are obtained from realistic disordered calculations, where the topological properties of the disordered systems are understood from a statistical point of view. Based on these calculations, x_c is around 17% for (Bi_(1-x)In_x)_2Se_3 but as high as 78%-83% for (Bi_(1-x)Sb_x)_2Se_3. In (Bi_(1-x)Sb_x)_2Se_3, we find that the phase transition is dominated by the decrease of SOC, with a crossover or "critical plateau" observed from around 78% to 83%. On the other hand, for (Bi_(1-x)In_x)_2Se_3, the In 5_s orbitals suppress the topological band inversion at low-impurity concentration, therefore accelerating the phase transition. In (Bi_(1-x)In_x)_2Se_3 we also find a tendency of In atoms to segregate.
机译：我们研究了Bi_2Se_3晶体结构中从x到（Bi_（1-x）In_x）_2Se_3和（Bi_（1-x）Sb_x）_2Se_3浓度为x的拓扑到正常绝缘体的相变。我们对小型超级细胞进行第一性原理计算，并使用此信息建立Wannierized有效哈密顿量，以更实际地治疗疾病。尽管In和Sb中的自旋轨道耦合（SOC）强度相似，但我们发现（Bi_（1-x）In_x）_2Se_3中的临界浓度x_c比（Bi_（1-x）中的临界浓度小得多Sb_x）_2Se_3例如，直接超级电池计算表明，两种合金的x_c分别低于12.5％和87.5％。从现实的无序计算中可以获得更准确的结果，从统计的角度了解无序系统的拓扑特性。基于这些计算，对于（Bi_（1-x）In_x）_2Se_3，x_c约为17％，但对于（Bi_（1-x）Sb_x）_2Se_3，x_c高达78％-83％。在（Bi_（1-x）Sb_x）_2Se_3中，我们发现相变以SOC的降低为主导，观察到交叉或“临界平台”从大约78％到83％。另一方面，对于（Bi_（1-x）In_x）_2Se_3，In 5_s轨道抑制了低杂质浓度下的拓扑带反转，因此加速了相变。在（Bi_（1-x）In_x）_2Se_3中，我们还发现In原子偏析的趋势。

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