外延1T'-WSe$_2$单层的鲁棒库仑能隙与变温研究
Robust Coulomb Gap and Varied-temperature Study of Epitaxial 1T'-WSe$_2$ Monolayers
AI总结：
本文通过变温ARPES和STS研究外延1T'-WSe$_2$单层的电子与晶体性质，发现BLG上样品具有显著热膨胀效应，而SrTiO$_3$上样品受衬底应变抑制变化，并证实库仑能隙可维持至200 K，为量子自旋霍尔器件应用提供依据。
摘要：
具有1T'结构相的过渡金属二硫族化合物（TMDCs）被预测在零温下是二维拓扑绝缘体。尽管1T'-WTe$_2$的量子化边缘电导已被证实可在高达100 K的温度下保持，但这一温度对于工业应用而言仍然相对较低。针对1T'-TMDCs中温度效应研究有限的问题，我们的研究聚焦于在双层石墨烯（BLG）和SrTiO$_3$(100)衬底上生长的外延1T'-WSe$_2$单层在不同温度下的电子与晶体性质。对于生长在BLG上的1T'-WSe$_2$，我们观察到其能带结构存在显著的热膨胀效应，热膨胀系数约为60×10$^{-6}$ K$^{-1}$。相比之下，生长在SrTiO$_3$(100)上的1T'-WSe$_2$由于衬底施加的增强应变，随温度变化表现出极小的改变。此外，在角分辨光电子能谱（ARPES）和扫描隧道谱（STS）中观察到钉扎在费米能级处的显著库仑能隙（CG）。研究发现该库仑能隙随温度升高而减小，并且对于1T'-WSe$_2$/BLG可以持续存在至200 K，这与我们的蒙特卡洛模拟结果一致。库仑能隙的鲁棒性以及正的体能隙赋予外延1T'-WSe$_2$单层在实现量子自旋霍尔器件方面的巨大潜力。
英文摘要：
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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