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.

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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