Hesp Niels C H, Torre Iacopo, Barcons-Ruiz David, Herzig Sheinfux Hanan, Watanabe Kenji, Taniguchi Takashi, Krishna Kumar Roshan, Koppens Frank H L
ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain.
Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki, Japan.
Nat Commun. 2021 Mar 12;12(1):1640. doi: 10.1038/s41467-021-21862-5.
Graphene-based moiré superlattices have recently emerged as a unique class of tuneable solid-state systems that exhibit significant optoelectronic activity. Local probing at length scales of the superlattice should provide deeper insight into the microscopic mechanisms of photoresponse and the exact role of the moiré lattice. Here, we employ a nanoscale probe to study photoresponse within a single moiré unit cell of minimally twisted bilayer graphene. Our measurements reveal a spatially rich photoresponse, whose sign and magnitude are governed by the fine structure of the moiré lattice and its orientation with respect to measurement contacts. This results in a strong directional effect and a striking spatial dependence of the gate-voltage response within the moiré domains. The spatial profile and carrier-density dependence of the measured photocurrent point towards a photo-thermoelectric induced response that is further corroborated by good agreement with numerical simulations. Our work shows sub-diffraction photocurrent spectroscopy is an exceptional tool for uncovering the optoelectronic properties of moiré superlattices.
基于石墨烯的莫尔超晶格最近已成为一类独特的可调节固态系统，展现出显著的光电活性。在超晶格的长度尺度上进行局部探测，应能更深入地了解光响应的微观机制以及莫尔晶格的确切作用。在此，我们采用纳米尺度探针来研究最小扭曲双层石墨烯单个莫尔晶胞内的光响应。我们的测量揭示了空间上丰富的光响应，其符号和大小由莫尔晶格的精细结构及其相对于测量接触的取向所决定。这导致了强烈的方向效应以及莫尔畴内栅极电压响应显著的空间依赖性。测量的光电流的空间分布和载流子密度依赖性指向光热电诱导响应，与数值模拟的良好吻合进一步证实了这一点。我们的工作表明，亚衍射光电流光谱是揭示莫尔超晶格光电特性的卓越工具。
