Ultrafast switching of topological invariants by light-driven interlayer vibrations

We investigate the high-speed topological phase transition driven by photoinduced interlayer vibrations at ambient conditions (room temperature and normal pressure). By employing ultrafast optical and THz spectroscopy, which enables us possible to study interlayer vibrations through photoelastic effects and topological surface state leading to low-energy conductivity in topological insulator Bi2Se3, we found that the interlayer vibrational mode, which originated from the confinement of photoinduced longitudinal strain waves, can drive the topological phase switching from topological insulator toward normal insulator. Our observations provide fundamental insights into nanomechanical interaction between lattice-topological phase for possible optoelectronic and spintronic applications based on all-optical topological phase switching at ultrafast timescales.