Abstract
MnBi2Te4 is a magnetic topological insulator with layered A-type antiferromagnetic order. It exhibits a rich layer- and magnetic-state dependent topological phase diagram; however, much about the coupling between spin, charge, and lattice remains to be explored. In this work, we report that MnBi2Te4 is an excellent acoustic phonon cavity by realizing phonon frequency combs using picosecond ultrasonics. With the generated acoustic phonon wavepackets, we demonstrate that the timing and phase of acoustic echoes can be used to detect the presence of stacking faults between van der Waals layers buried deep within the crystal. Furthermore, by implementing this nondestructive ultrafast optical measurement in conjunction with time-resolved magneto-optical Kerr effect experiments, we uncover that out-of-plane vibrations in MnBi2Te4 do not couple to the magnetic order, i.e. there is no appreciable magnetostriction. Our work points out how a well-developed technique can probe the structural defects and phonon pulse engineering in layered topological insulators.
Original language | English |
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Pages (from-to) | 10562-10568 |
Number of pages | 7 |
Journal | Nano Letters |
Volume | 24 |
Issue number | 34 |
DOIs | |
State | Published - Aug 28 2024 |
Funding
We thank Ellis Thompson for thoughtful feedback during the preparation of this manuscript. This work was mainly supported by the Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division (DE-SC0012509). Sample fabrication and optical measurements are partially supported by AFOSR FA9550-21-1-0460 and FA9550-21-1-0177. J.Y. acknowledges support from the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. The authors also acknowledge the use of the facilities and instrumentation supported by NSF MRSEC DMR-1719797. This research was supported by an appointment to the Intelligence Community Postdoctoral Research Fellowship Program at the University of Washington, administered by Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and the Office of the Director of National Intelligence. X.X. acknowledges the support from the State of Washington funded Clean Energy Institute.
Keywords
- MnBiTe
- magnetostriction
- picosecond ultrasonics
- stacking defect
- van der Waals