Electronic structures and photoemission spectroscopy

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Unveiling a Tunable Moir茅 Bandgap in Bilayer Graphene/hBN Device by Angle鈥怰esolved Photoemission Spectroscopy

Advanced Science Wiley (2025) 2412609

Authors:

Hanbo Xiao, Han Gao, Min Li, Fanqiang Chen, Qiao Li, Yiwei Li, Can Li, Meixiao Wang, Fangyuan Zhu, Lexian Yang, Shiyong Wang, Feng Miao, Yulin Chen, Cheng Chen, Bin Cheng, Jianpeng Liu, Zhongkai Liu

Abstract:

Over the years, great efforts have been devoted in introducing a sizable and tunable band gap in graphene for its potential application in next鈥恎eneration electronic devices. The primary challenge in modulating this gap has been the absence of a direct method for observing changes of the band gap in momentum space. In this study, advanced spatial鈥 and angle鈥恟esolved photoemission spectroscopy technique is employed to directly visualize the gap formation in bilayer graphene, modulated by both displacement fields and moir茅 potentials. The application of displacement field via in situ electrostatic gating introduces a sizable and tunable electronic bandgap, proportional to the field strength up to 100 meV. Meanwhile, the moir茅 potential, induced by aligning the underlying hexagonal boron nitride substrate, extends the bandgap by 鈮20 meV. Theoretical calculations effectively capture the experimental observations. This investigation provides a quantitative understanding of how these two mechanisms collaboratively modulate the band gap in bilayer graphene, offering valuable guidance for the design of graphene鈥恇ased electronic devices.

Gate-Controlled Superconducting Switch in GaSe/NbSe2 van der Waals Heterostructure

ACS Nano American Chemical Society (ACS) 19:1 (2025) 1295-1301

Authors:

Yifan Ding, Chenyazhi Hu, Wenhui Li, Lan Chen, Jiadian He, Yiwen Zhang, Xiaohui Zeng, Yanjiang Wang, Peng Dong, Jinghui Wang, Xiang Zhou, Yueshen Wu, Yulin Chen, Jun Li

Thickness-dependent topological phases and flat bands in rhombohedral multilayer graphene

Science Bulletin Elsevier (2025)

Authors:

Hanbo Xiao, Cheng Chen, Xin Sui, Shihao Zhang, Mengzhao Sun, Han Gao, Qi Jiang, Qiao Li, Lexian Yang, Mao Ye, Fangyuan Zhu, Meixiao Wang, Jianpeng Liu, Zhibin Zhang, Zhujun Wang, Yulin Chen, Kaihui Liu, Zhongkai Liu

Layer-dependent exciton dynamics in InSe/WS2 heterostructures

CHINESE PHYSICS B 34:9 (2025) ARTN 097802

Authors:

Siyao Li, Yufan Wang, Zhiqiang Ming, Yong Liu, Lanyu Huang, Siman Liu, Jialong Liu, Yulin Chen, Zhoujuan Xu, Zeyu Liu, Danliang Zhang, Xiao Wang

Topological phase transition in quasi-one-dimensional bismuth iodide Bi 4 I 4

npj Quantum Materials Nature Research 9:1 (2024) 103

Authors:

WX Zhao, M Yang, X Du, YD Li, KY Zhai, YQ Hu, JF Han, Y Huang, ZK Liu, YG Yao, JC Zhuang, Y Du, JJ Zhou, YL Chen, LX Yang

Abstract:

Quasi-one-dimensional (quasi-1D) bismuth iodide Bi4I4 exhibits versatile topological phases of matter including weak topological insulator (WTI) and higher-order topological insulator (HOTI) phases with high tunability in response to external parameters. In this work, performing laser-based angle-resolved photoemission spectroscopy with submicron spatial resolution (micro-ARPES), we reveal the presence of an energy gap on the (100) surface of the low-temperature 伪-Bi4I4, providing spectroscopic evidence for the HOTI phase. Conversely, the high-temperature 尾-Bi4I4 harbors gapless Dirac fermions on the (100) surface alongside gapped states on the (001) surface, thereby establishing a WTI phase. By tracking the temperature evolution of the (100) surface states, we unveil a thermal hysteresis of the surface gap in line with the 伪-尾 structural phase transition. Our findings directly evidence a temperature-induced topological phase transition from WTI to HOTI in Bi4I4, which paves the way to its potential applications at room temperature.