ausblenden:
Schlagwörter:
Condensed Matter, Materials Science, cond-mat.mtrl-sci
Zusammenfassung:
Two-dimensional twisted bilayer moiré structures provide a versatile material platform for realizing a rich variety of strongly correlated electronic quantum phases intricately coupled with the periodically modulated lattice structures. In this work, we use ultrafast electron diffraction to directly reveal the photoinduced dynamic evolution of the moiré superlattice in 2∘ and 57∘ twisted WSe2/MoSe2 heterobilayers. Upon above-band-gap photoexcitation, the moiré superlattice diffraction features are enhanced within 1 ps and subsequently suppressed several picoseconds after, accompanied by a collective lattice excitation of a moiré phonon mode with sub-THz frequency. This unique response deviates markedly from typical photoinduced lattice heating, and suggests dynamic twisting and untwisting of the local moiré chiral structure. We infer large oscillations in the local twist angle, approaching 1∘ peak to trough, that are driven by ultrafast charge carrier excitation and relaxation -- a phenomenon further supported by molecular dynamics simulations. Our findings suggest a novel approach for real-time dynamic reconfiguration of moire superlattices to achieve ultrafast modulation of their strongly correlated behaviors.
