Atom-by-atom imaging of moiré phasons with electron ptychography

• 成果类型: Article
• 署名作者: Zhang, Yichao; Ahammed, Ballal; Bae, Sang Hyun; Lee, Chia-Hao; Huang, Jeffrey; Hossain, Mohammad Abir; Rakib, Tawfiqur; van der Zande, Arend M.; Ertekin, Elif; Huang, Pinshane Y.
• 署名单位: University of Illinois System; University of Illinois Urbana-Champaign; University of Illinois System; University of Illinois Urbana-Champaign; University System of Maryland; University of Maryland College Park; University of Illinois System; University of Illinois Urbana-Champaign; University of Illinois System; University of Illinois Urbana-Champaign
• 刊物名称: SCIENCE
• ISSN/ISSBN: 0036-12979
• DOI: 10.1126/science.adw7751
• 发表日期: 2025-07-24
• 页码: 423-428
• 关键词: microscopy

摘要

Twisted two-dimensional materials exhibit distinctive vibrational modes called moir & eacute; phonons, which arise from the moir & eacute; superlattice. Here, we demonstrate atom-by-atom imaging of phasons, an ultrasoft class of moir & eacute; phonons in twisted bilayer tungsten diselenide (WSe2). Using ultrahigh-resolution (<15 picometers) electron ptychography, we imaged the size and shape of each atom to extract time-averaged vibrational amplitudes as a function of twist angle and position. We observed several signature properties of moire phasons, such as increased vibrational amplitudes at solitons and AA-stacked regions. By correlating experiments with molecular dynamics simulations and lattice dynamics calculations, we show that phasons dominate the thermal vibrations in low-angle twisted bilayers. These results represent a powerful route to image thermal vibrations at atomic resolution, unlocking experimental studies of a thus far hidden branch of moir & eacute; phonon physics.