Observation of topological edge states in the quantum spin Hall insulator <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi>Ta</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mi>Pd</mml:mi></mml:mrow><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mi>Te</mml:mi></mml:mrow><mml:mn>5</mml:mn></mml:msub></mml:math>
Xuguang Wang, Daiyu Geng, Dayu Yan, Wenqi Hu, Hexu Zhang, Shaosheng Yue, Zhenyu Sun, Shiv Kumar, Eike F. Schwier, K. Shimada, Peng Cheng, Lan Chen, Simin Nie, Zhijun Wang, Youguo Shi, Yi‐Qi Zhang, Kehui Wu, Baojie Feng
Abstract
Two-dimensional topological insulators (2DTIs), which host the quantum spin Hall (QSH) effect, are one of the key materials in next-generation spintronic devices. To date, experimental evidence of the QSH effect has only been observed in a few materials, and thus, the search for new 2DTIs is at the forefront of physical and materials science. Here, we report experimental evidence of a 2DTI in the van der Waals material ${\mathrm{Ta}}_{2}{\mathrm{Pd}}_{3}{\mathrm{Te}}_{5}$. First-principles calculations show that each monolayer of ${\mathrm{Ta}}_{2}{\mathrm{Pd}}_{3}{\mathrm{Te}}_{5}$ is a 2DTI with weak interlayer interactions. Combined transport, angle-resolved photoemission spectroscopy, and scanning tunneling microscopy measurements confirm the existence of a band gap at the Fermi level and topological edge states inside the gap. These results demonstrate that ${\mathrm{Ta}}_{2}{\mathrm{Pd}}_{3}{\mathrm{Te}}_{5}$ is a promising material for fabricating spintronic devices based on the QSH effect.