Fang Liu [Stanford University]

Abstract: 

Two-dimensional (2D) materials and their twisted superlattices offer exciting opportunities for next-generation electronic, optoelectronic, and electrochemical devices. Yet, studies of high-quality heterostructures have been largely constrained to microscopic flakes. Here, we present scalable, controllable top-down methods that transform a wide range of van der Waals (vdW) single crystals into twisted moiré superlattices with high yield, exceptional uniformity, and macroscopic dimensions from millimeters to centimeters. Access to such large-area structures has enabled new discoveries, including rapid photoinduced twisting and untwisting of moiré patterns, momentum-resolved phonon dynamics upon photoexcitation, and high-resolution imaging of backfolded moiré miniband structure with energy, momentum and spin polarization. Furthermore, by patterning 1D features—such as nanoribbon arrays and nanowrinkles—on 2D monolayers, we uncover unique electronic and thermodynamic behaviors absent in pristine layers. These advances in large-scale 2D artificial structures pave the way toward mass production and commercialization of 2D devices.

Research interests: 

moire superlattices; angle-resolved photoemission spectroscopy, 2D materials, ultrafast spectroscopy