Han Tianyi, Yang Jixiang, Zhang Qihang, Wang Lei, Watanabe Kenji, Taniguchi Takashi, McEuen Paul L, Ju Long
Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA.
Phys Rev Lett. 2021 Apr 9;126(14):146402. doi: 10.1103/PhysRevLett.126.146402.
Monolayer graphene aligned with hexagonal boron nitride (h-BN) develops a gap at the charge neutrality point (CNP). This gap has previously been extensively studied by electrical transport through thermal activation measurements. Here, we report the determination of the gap size at the CNP of graphene/h-BN superlattice through photocurrent spectroscopy study. We demonstrate two distinct measurement approaches to extract the gap size. A maximum of ∼14 meV gap is observed for devices with a twist angle of less than 1°. This value is significantly smaller than that obtained from thermal activation measurements, yet larger than the theoretically predicted single-particle gap. Our results suggest that lattice relaxation and moderate electron-electron interaction effects may enhance the CNP gap in graphene/h-BN superlattice.
与六方氮化硼（h-BN）对齐的单层石墨烯在电荷中性点（CNP）处会形成一个能隙。此前，人们通过热激活测量的电输运对这个能隙进行了广泛研究。在此，我们报告通过光电流光谱研究确定石墨烯/h-BN超晶格CNP处的能隙大小。我们展示了两种不同的测量方法来提取能隙大小。对于扭转角小于1°的器件，观察到最大约14 meV的能隙。这个值明显小于通过热激活测量得到的值，但大于理论预测的单粒子能隙。我们的结果表明，晶格弛豫和适度的电子-电子相互作用效应可能会增强石墨烯/h-BN超晶格中的CNP能隙。
