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arXiv · 2409.09698

Robust Coulomb Gap and Varied-temperature Study of Epitaxial 1T'-WSe$_2$ Monolayers

Wang Chen·Mengli Hu·Junyu Zong·Xuedong Xie·Wei Ren·Qinghao Meng·Fan Yu·Qichao Tian·Shaoen Jin·Xiaodong Qiu·Kaili Wang·Can Wang·Junwei Liu·Fang-Sen Li·Li Wang·Yi Zhang
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Abstract

The transition metal dichalcogenides (TMDCs) with a 1T' structural phase are predicted to be two-dimensional topological insulators at zero temperature. Although the quantized edge conductance of 1T'-WTe$_2$ has been confirmed to survive up to 100 K, this temperature is still relatively low for industrial applications. Addressing the limited studies on temperature effects in 1T'-TMDCs, our research focuses on the electronic and crystal properties of the epitaxial 1T'-WSe$_2$ monolayers grown on bilayer graphene (BLG) and SrTiO$_3$(100) substrates at various temperatures. For the 1T'-WSe$_2$ grown on BLG, we observed a significant thermal expansion effect on its band structures with a thermal expansion coefficient of $\sim$60$\times$10$^{-6}$ K$^{-1}$. In contrast, the 1T'-WSe$_2$ grown on SrTiO$_3$(100) exhibits minimal changes with varied temperatures due to the enhanced strain exerted by the substrate. Besides, A significant Coulomb gap (CG) was observed pinned at the Fermi level in the angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling spectroscopy (STS). The CG was founded to decrease with increasing temperatures, and can persist up to 200 K for 1T'-WSe$_2$/BLG, consistent with our Monte Carlo simulations. The robustness of the CG and the positive fundamental gap endow the epitaxial 1T'-WSe$_2$ monolayers with huge potential for realizing the quantum spin Hall devices.

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Wang Chen, Mengli Hu, Junyu Zong, Xuedong Xie, Wei Ren, Qinghao Meng, Fan Yu, Qichao Tian, Shaoen Jin, Xiaodong Qiu, Kaili Wang, Can Wang, Junwei Liu, Fang-Sen Li, Li Wang, Yi Zhang. 2024-09-15. Robust Coulomb Gap and Varied-temperature Study of Epitaxial 1T'-WSe$_2$ Monolayers. https://doi.org/10.1021/acs.jpclett.4c03573

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