Experimental observation of edge-dependent quantum pseudospin Hall effect

Huanhuan Yang, Lingling Song, Yunshan Cao, X. R. Wang, and Peng Yan

Phys. Rev. B 104, 235427 – Published 22 December 2021

Abstract

It is conventional wisdom that the helical edge states of a quantum spin Hall (QSH) insulator are particularly stable due to the topological protection of time-reversal symmetry. Here, we report experimental observation of an edge-dependent quantum (pseudo)spin Hall effect by employing two Kekulé electric circuits with molecule-zigzag and partially bearded edges, where the chirality of the circulating current in the unit cell mimics the electron spin. We observe a helicity flipping of the topological in-gap modes emerging in opposite parameter regions for the two edge geometries. Experimental findings are interpreted in terms of the mirror winding number defined in the unit cell, the choice of which exclusively depends on the edge shape. Our work offers a deeper understanding of the boundary effect on the QSH phase and paves the way for studying the spin-dependent topological physics in electric circuits.

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Received 12 January 2021
Revised 16 July 2021
Accepted 13 December 2021

DOI:https://doi.org/10.1103/PhysRevB.104.235427

Physics Subject Headings (PhySH)

Hall effect Symmetry protected topological states Topological insulators Topological phase transition Topological phases of matter

Tight-binding model

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Huanhuan Yang ¹, Lingling Song¹, Yunshan Cao¹, X. R. Wang^2,*, and Peng Yan ^1,†

¹School of Electronic Science and Engineering and State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
²Physics Department, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong

^*Corresponding author: phxwan@ust.hk
^†Corresponding author: yan@uestc.edu.cn

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Vol. 104, Iss. 23 — 15 December 2021

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