中山大学王成新团队报道了显示二次谐波产生、线性温度电阻率和弱反局域化的不寻常的Janus Bi₂TeSe₂拓扑绝缘体。相关研究成果发表在2024年6月25日出版的《美国化学会杂志》。

关于反转对称Bi₂Te_xSe_3–x拓扑绝缘体的公认是有前景的新一代量子器件的特点。值得注意的是，包含不同表面电子结构的反转不对称相可能会产生一种额外的拓扑现象，指向一种新的器件范式。

该文中，研究人员通过化学气相沉积生长实现了具有Se–Bi–Se–Bi–Te非常规堆叠序列的Janus Bi₂TeSe₂单晶纳米片，并通过原子分辨AC-STEM和元素图谱进行了阐明。由于该系统中平面镜对称性的破坏，检测到具有代表性的6倍旋转对称性的明显的偏振相关二次谐波产生。低温输运测量显示出一种奇怪的金属状温度电阻率线性。

揭示了由拓扑表面态的弱反局域化效应和二维输运主导的，各向异性磁阻引起的低磁场下的异常电导峰。这些发现将Janus Bi₂TeSe₂相与新兴的物理主题联系起来，这将激发对发展良好的Bi₃Te_xSe_3–x拓扑绝缘体的新思考，并为探索混合非线性光电拓扑器件开辟机会。

附：英文原文

Title: Unusual Janus Bi2TeSe2 Topological Insulators Displaying Second-Harmonic Generation, Linear-in-Temperature Resistivity, and Weak Antilocalization

Author: Xiaobin Zou, Xuanhao Yuan, Lishan Liang, Fei Tian, Yan Li, Yong Sun, Chengxin Wang

Issue&Volume: June 25, 2024

Abstract: Well-established knowledge about inversion-symmetric Bi2TexSe3–x topological insulators characterizes the promising new-generation quantum device. Noticeably, the inversion asymmetric phase containing different surface electronic structures may create an extra topological phenomenon pointing to a new device paradigm. Herein, Janus Bi2TeSe2 single-crystal nanosheets with an unconventional stacking sequence of Se–Bi–Se–Bi–Te are realized via chemical vapor deposition growth, which is clarified by atomically resolved AC-STEM and elemental mapping. An obvious polarization-dependent second-harmonic generation with a representative 6-fold rotational symmetry is detected due to the broken out-of-plane mirror symmetry in this system. Low-temperature transport measurements display a strange metal-like linear-in-temperature resistivity. Anomalous conductance peaks under low magnetic fields induced by the weak antilocalization effect of topological surface states and the two-dimensional transport-dominated anisotropic magnetoresistance are revealed. These findings correlate the Janus Bi2TeSe2 phase with emerging physics topics, which would inspire fresh thoughts in well-developed Bi3TexSe3–x topological insulators and open up opportunities for exploring hybrid nonlinear optoelectronic topological devices.

DOI: 10.1021/jacs.4c03176

Source: https://pubs.acs.org/doi/abs/10.1021/jacs.4c03176