Vashist Amit, Gopal R K, Singh Yogesh
Department of Physical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Knowledge City, Sector 81, Mohali, 140306 India.
Sci Rep. 2021 Apr 22;11(1):8756. doi: 10.1038/s41598-021-87780-0.
Bi[Formula: see text]Sb[Formula: see text] is a topological insulator (TI) for [Formula: see text]-0.20. Close to the Topological phase transition at [Formula: see text], a magnetic field induced Weyl semi-metal (WSM) state is stabilized due to the splitting of the Dirac cone into two Weyl cones of opposite chirality. A signature of the Weyl state is the observation of a Chiral anomaly [negative longitudinal magnetoresistance (LMR)] and a violation of the Ohm's law (non-linear [Formula: see text]). We report the unexpected discovery of Chiral anomaly-like features in the whole range ([Formula: see text]) of the TI state. This points to a field induced WSM state in an extended x range and not just near the topological transition at [Formula: see text]. Surprisingly, the strongest Weyl phase is found at [Formula: see text] with a non-saturating negative LMR much larger than observed for [Formula: see text]. The negative LMR vanishes rapidly with increasing angle between B and I. Additionally, non-linear I-V is found for [Formula: see text] indicating a violation of Ohm's law. This unexpected observation of a strong Weyl state in the whole TI regime in Bi[Formula: see text]Sb[Formula: see text] points to a gap in our understanding of the detailed crystal and electronic structure evolution in this alloy system.
对于(x = -0.20)，Bi[公式：见原文]Sb[公式：见原文]是一种拓扑绝缘体（TI）。在(x)接近拓扑相变时，由于狄拉克锥分裂成两个具有相反手性的外尔锥，磁场诱导的外尔半金属（WSM）态得以稳定。外尔态的一个特征是观察到手征反常[负纵向磁阻（LMR）]和欧姆定律的违反（非线性(I-V)）。我们报告了在TI态的整个范围（(x)）中意外发现的类似手征反常的特征。这表明在扩展的(x)范围内存在场诱导的WSM态，而不仅仅是在(x)处的拓扑相变附近。令人惊讶的是，最强的外尔相发现在(x)处，其不饱和负LMR比(x)处观察到的大得多。负LMR随着(B)和(I)之间夹角的增加而迅速消失。此外，对于(x)发现了非线性(I-V)，表明违反了欧姆定律。在Bi[公式：见原文]Sb[公式：见原文]的整个TI区域中意外观察到强外尔态，这表明我们对该合金系统中详细的晶体和电子结构演化的理解存在差距。
