As a 3D topological insulator, bismuth selenide (Bi2Se3) has potential applications for electrically and optically controllable magnetic and optoelectronic devices. Understanding the coupling with its topological phase requires studying the interactions of carriers with the lattice on time scales down to the subpicosecond regime. Here, we investigate the ultrafast carrier-induced lattice contractions and interlayer modulations in Bi2Se3 thin films by time-resolved diffraction using an X-ray free-electron laser. The lattice contraction depends on the carrier concentration and is followed by an interlayer expansion accompanied by oscillations. Using density functional theory and the Lifshitz model, the initial contraction can be explained by van der Waals force modulation of the confined free carrier layers. Our theoretical calculations suggest that the band inversion, related to a topological phase transition, is modulated by the expansion of the interlayer distance. These results provide insights into the topological phase control by light-induced structural change on ultrafast time scales.
Bibliographical noteFunding Information:
We thank Sanghoon Song and Aymeric Robert for fruitful discussions. This research was supported by the National Research Foundation of Korea (NRF-2015R1A5A1009962, 2019R1A6B2A02100883, and 2021R1A3B1077076). Y.K. and E.S. acknowledge the support from NRF-2020R1A2C2007468. H.W. acknowledges the support of U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. This research used resources of the Advanced Photon Source, a U.S. DOE Office of Science User Facility, operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. The experiments were carried out at the XSS beamline of PAL-XFEL (experiment no. 2017-1st-FXS-006 and 2018-1st-XSS-010) funded by the Ministry of Science and ICT of Korea. The work at MIT was supported by the Center for Integrated Quantum Materials (NSF-DMR 1231319), the NSF Grant No. DMR 1700137, NSF CONVERGENCE ACCELERATOR TRACK C: SYN OIA-2040620, and ONR Grant Nos. N00014-16-1-2657 and N00014-20-1-2306.
© 2021 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanical Engineering