Observation of 450 GHz surface acoustic waves in suspended polycrystalline films by use of time-resolved resonant soft X-ray scattering

ORAL

Abstract

We have used ultrafast optical pumping to generate nanoscale surface acoustic waves (SAWs) from 200 to 450 GHz, 10-50 nm wavelengths, in metallic films on SiN membranes. Our measurement demonstrates a novel soft X-ray elastic scattering mechanism that probes the coupling of the electronic and phononic degrees of freedom on a [Co90Fe10(0.6 nm)/Ni(0.2 nm)]x50 multilayer. The samples have an average grain size of 30 nm and a rms roughness of 1 nm. This nanostructured surface topography allows optical coupling to the in-plane SAW. In a transmission soft X-ray scattering geometry, with circular polarized X-rays tuned to the Ni L3edge, we observe a prominent charge scatter ring with a radius of approximately 0.2 nm-1. After optical pumping with fluences ranging from 24-27 mJ/cm2, SAWs appeared as ripples on the charge scatter ring that oscillate at ps timescales. We use Brillouin light scattering (BLS) and modeling to identify the SAW as a dilation mode with an in-plane velocity of 5.6 km/s. Surprisingly, the SAW lifetime peaks sharply at q = 0.25 nm-1(300 GHz), with a value greater than 60 ps, suggestive of a minimum in the SAW correlation length in the case of 2-d localization.

*Support by DOE/BES X-Ray Scattering Program Awards No. DE-SC0002002, DE-SC0018237, and DE-FOA-0001664

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Presenters

  • Thomas Silva

    • National Institute of Standards and Technology Boulder
    • NIST
    • Quantum Electromagnetics Division, NIST, Boulder, CO, United States
    • National Institute of Standards and Technology, Boulder CO

Authors

  • Phoebe Tengdin

    • Physics, University of Colorado
    • JILA, University of Colorado Boulder
    • University of Colorado, Boulder / JILA
    • JILA, University of Colorado, Boulder

  • Dmitriy Zusin

    • Physics, University of Colorado
    • JILA, University of Colorado Boulder
    • University of Colorado, Boulder / JILA
    • JILA, University of Colorado, Boulder

  • Joshua L Knobloch

    • Physics, University of Colorado

  • Anatoly Shabalin

    • University of California, San Diego
    • Physics, University of California, San Diego
    • University of California San Diego

  • Stjepan Hrkac

    • University of California, San Diego
    • Physics, University of California, San Diego
    • University of California San Diego

  • Nelson Hua

    • University of California, San Diego
    • Physics, University of California, San Diego
    • University of California San Diego

  • Yaroslav Kvashnin

    • Physics and Astronomy, Uppsala University
    • Uppsala University

  • Sheena Patel

    • Physics, University of California, San Diego
    • University of California San Diego

  • TianMin Liu

    • Physics, Stanford University
    • Stanford University / LCLS, Menlo Park, CA, United States

  • Justin Shaw

    • Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, Colorado 80305, USA
    • National Institute of Standards and Technology Boulder
    • Quantum Electromagnetics Division, NIST, Boulder, CO, United States
    • National Institute of Standards and Technology, Boulder CO

  • Hans T. Nembach

    • Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, Colorado 80305, USA
    • National Institute of Standards and Technology Boulder
    • JILA, University of Colorado, Boulder
    • Quantum Electromagnetics Division, NIST, Boulder, CO, United States
    • National Institute of Standards and Technology, Boulder CO

  • Daniel J Higley

    • Physics, Stanford University
    • Stanford University / LCLS, Menlo Park, CA, United States

  • William F Schlotter

    • SLAC National Accelerator Laboratory
    • SLAC
    • SLAC National Accelerator Laboratory, Menlo Park, CA, United States

  • Alex Reid

    • SLAC National Accelerator Laboratory
    • SLAC
    • SLAC National Accelerator Laboratory, Menlo Park, CA, United States

  • Rahul Nandkishore

    • University of Colorado, Boulder
    • Physics, University of Colorado, Boulder
    • Department of Physics, University of Colorado Boulder
    • Physics, University of Colorado

  • Olle Eriksson

    • Uppsala University
    • Uppsala University and Örebro University
    • Physics and Astronomy, Uppsala University

  • Löic Le Guyader

    • European XFEL
    • European X-Ray Free-Electron Laser Facility GmbH

  • Eric Fullerton

    • Electrical and Computer Engineering, University of California San Diego
    • University of California, San Diego
    • Center for Memory and Recording Research, Univesrity of California, San Diego
    • Electrical and Computer Engineering, University of California, San Diego
    • University of California San Diego

  • Oleg Shpyrko

    • University of California, San Diego
    • Physics, University of California, San Diego

  • Margaret Mary Murnane

    • JILA, University of Colorado, Boulder
    • JILA, University of Colorado Boulder
    • Department of Physics and JILA, University of Colorado, Boulder
    • University of Colorado, Boulder / JILA
    • University of Colorado, Boulder

  • Henry C Kapteyn

    • JILA, University of Colorado, Boulder
    • JILA, University of Colorado Boulder
    • Department of Physics and JILA, University of Colorado, Boulder
    • University of Colorado, Boulder / JILA
    • University of Colorado, Boulder

  • Hermann Dürr

    • Uppsala University
    • Physics and Astronomy, Uppsala University

  • Thomas Silva

    • National Institute of Standards and Technology Boulder
    • NIST
    • Quantum Electromagnetics Division, NIST, Boulder, CO, United States
    • National Institute of Standards and Technology, Boulder CO