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Title: Anisotropic structural dynamics of monolayer crystals revealed by femtosecond surface X-ray scattering

Journal Article · · Nature Photonics
 [1]; ORCiD logo [2];  [1];  [1];  [1]; ORCiD logo [3];  [3];  [4];  [4];  [5];  [6];  [6];  [6]; ORCiD logo [6];  [6];  [7];  [7];  [2];  [2];  [1] more »;  [8]; ORCiD logo [2]; ORCiD logo [3];  [8]; ORCiD logo [1] « less
  1. Argonne National Lab. (ANL), Argonne, IL (United States)
  2. Univ. of Southern California, Los Angeles, CA (United States)
  3. Univ. of Washington, Seattle, WA (United States)
  4. Stanford Univ., CA (United States)
  5. Stanford Univ., CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States). Photon Ultrafast Laser Science and Engineering Inst. (PULSE)
  6. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  7. Kumamoto Univ., Kumamoto (Japan)
  8. Stanford Univ., CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States). Photon Ultrafast Laser Science and Engineering Inst. (PULSE); SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Institute for Materials and Energy Science (SIMES)

Ultrafast X-ray scattering is one of the primary tools to track intrinsic crystallographic evolution with atomic accuracy in real time. However, its application to study nonequilibrium structural properties at the two-dimensional limit remains a long-standing challenge due to a significant reduction of diffraction volume and complexity of data analysis. Here, we report femtosecond surface X-ray diffraction in combination with crystallographic model-refinement calculations to quantify the ultrafast structural dynamics of monolayer WSe2 crystals supported on a substrate. We found the absorbed optical photon energy is preferably coupled to the in-plane lattice vibrations within one picosecond whereas the out-of-plane lattice vibration amplitude remains unchanged during the first ten picoseconds. The model-assisted fitting suggests an asymmetric intralayer spacing change upon excitation. The observed nonequilibrium anisotropic structural dynamics agrees with first-principles modelling in both real and momentum space, marking the distinct structural dynamics of monolayer crystals from their bulk counterparts.

Research Organization:
SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
AC02-76SF00515
OSTI ID:
1532479
Journal Information:
Nature Photonics, Journal Name: Nature Photonics Journal Issue: 6 Vol. 13; ISSN 1749-4885
Publisher:
Nature Publishing GroupCopyright Statement
Country of Publication:
United States
Language:
English

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