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Mariano Trigo, PULSE, SLAC National Accelerator Laboratory

When:  Wednesday, April 9, 2014 at 3:00PM to 4:00 PM

Where: B901 Rm 108B – Redtail

I will show that broadband, hard x-ray pulses from LCLS can be used to
probe the vibrational spectrum (phonon dispersion) of a solid with
sub-meV energy resolution over the entire Brillouin zone. Our
pump-probe approach exploits a two-phonon mechanism to generate
coherent oscillations in the rms displacements (squeezed phonons)
across the entire Brillouin zone. The time-dependent rms displacements
are then measured via diffuse scattering with femtosecond hard-x-ray
pulses. The sub-meV resolution is achieved by a Fourier transform of
the oscillatory dynamics. Using this method we obtain the full
transverse acoustic phonon dispersion in germanium. I will discuss
some of the requirements for this approach, both in the generation of
coherent two-phonon states by ultrafast optical pulses and their
detection via x-ray scattering. I will finally comment on recent
results on the anharmonic phonons of thermoelectric PbTe using this
method.

More information

Mariano Trigo
Coherent phonon spectroscopy at LCLS: extreme frequency and momentum resolution with broadband pulses.