Planar Hall effect (PHE) in topological insulators (TIs) is discussed as an effect that stems mostly from conduction due to topologically protected surface states. Although surface states play a critical role and are of utmost importance in TIs, our present study in Bi₂Te₃ thin films reflects the need for considering the bulk conduction in understanding the origin of PHE in TIs. This necessity emerges from our observation of an unconventional increase in the PHE signal with TI thickness and temperature where the bulk effect takes over. Here, we find an enhancement in the PHE amplitude by doubling the Bi₂Te₃ film-thickness on the Si (111) substrate—from $\approx$ 1.9 nΩ m in 14 quintuple layer (QL) to $\approx$ 3.1 nΩ m in 30 QL devices at B = 5 T. Also, the PHE amplitude in the 30 QL Bi₂Te₃ films grown on two different substrates, viz., Si (111) and Al₂O₃ (0001), shows an increase with temperature. Our experiments indicate that the contribution of bulk states to PHE in TIs could be significant.

中文翻译：

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拓扑绝缘体——Bi2Te3 中平面霍尔效应的观察

拓扑绝缘体 (TI) 中的平面霍尔效应 (PHE) 被认为是一种主要源于受拓扑保护的表面状态导致的传导的效应。尽管表面态在 TI 中起着至关重要的作用并且是最重要的，但我们目前对 Bi ₂ Te ₃薄膜的研究反映了在理解 TI 中 PHE 起源时需要考虑体传导。这种必要性源于我们对 PHE 信号随 TI 厚度和温度的非常规增加的观察，其中体积效应接管了。在这里，我们发现通过将Si (111) 衬底上的Bi ₂ Te ₃薄膜厚度加倍，PHE 幅度得到了增强——从$\approx$ 14 个五重层 (QL) 中的 1.9 nΩ m $\approx$在 B = 5 T 时，30 个 QL 器件中的 3.1 nΩ m。此外，在两种不同衬底（即 Si (111) 和 Al ₂ O ₃ (0001)）上生长的 30 个 QL Bi ₂ Te ₃薄膜中的 PHE 振幅显示随温度升高。我们的实验表明，体态对 TI 中 PHE 的贡献可能是显着的。