UNIVERSITE Pierre & Marie CURIE

UNIVERSITE Pierre & Marie CURIE La science à PARIS "NANO-ACOUSTICS AND TERAHERTZ ACOUSTICS" Bernard Perrin International Workshop on « Nanoscale Energy Conversion and Information Processing Devices » - September 24-26, 2006, Nice - France -

Probing vibrations at the nanoscale Phonons : nm scale 10 LA neutron THz range TA 1,0 IXS Picosecond acoustics Ballistic phonon heat transport 10-1 10-2 Fréquency n (THz) Picosecond acoustics (H. Maris, 1985) Brillouin 10-3 nano-systems 10-4 10-5 piezo 10-4 10-3 10-2 10-1 1,0 Wavevector q/p (u.a.) Sound wave velocity in solids 5 – 10 nm/ps • What can be done with an optical pump probe technique to increase the frequency range of laser ultrasonics? • Phonon engineering • Phonon nanocavities

Lsubstrate > a few hundreds mm probe pump substrate Lfilm > a few tens nm reflectometry interferometry Nanometric sonar in thin films

Distorsion over large distance propagation ( > 0.1 mm) Lattice dispersion Lattice anharmonocity

Dispersion and nonlinearity : Solitons Non linearity Dispersion 150 fs (1.4nm) (MgO) Stable solution (soliton)

Rectangular initial strain Area conservation Multi-soliton formation

Acoustic Nonlinearity Non linearity 356 m probe GaAs pump Al-30 nm Al-30 nm [100] - Harmonic distorsion - sound velocity = f() - Acoustic rectification

Expérience de réflectométrie en fonction de la puissance d'excitation

Q longitudinal phonons tranverse phonons Black body radiation time Spectrum up to a few THz Z-cut in Sapphire - T = 3.8 K Ballistic propagation of heat pulses

GaAs/AlAs

First longitudinal coherent acoustic echo (one way trip) T = 15 K 356 m One way + 6 round trips One way + 2 round trips reflectometry probe GaAs interferometry pump Al-30 nm Al-30 nm [100] Can we do the same with a pump probe technique?

Q = 0.12 nJ Temperature dependence

pump probe at different locations 12 K - Q=0.6 nJ Al 30 nm Al 30 nm 1 vst. 3 13 0 m) m Heat pulse : moving acoustic source 30 Position ( vstvph : building up of a large matter displacement 60 vph. vph. 200 400 600 800 1000 1200 1400 Delay (ps) XY scan in the detection surface

Phonon engineering and acoustic nanocavity

Acoustic mirror Acoustic nanocavity

GaAs pump probe 356 µm Nanocavity used as a phonons generator cavity

Selective excitation of the cavity mode

GaAs probe pump Nanocavity or mirror used as a phonon detector 356 µm Acoustic mirror

Phonon engineering in the subterahertz range is possible • Semiconductor superlattices work as excellent acoustic Bragg mirrors • Acoustic nanocavity has been evidenced • A first step towards a SASER Laurent Belliard – INSP Alex Fainstein – Institut Balseiro (Bariloche) Agnès Huynh - INSP Bernard Jusserand - INSP Daniel Kimura- Lanzillotti (INSP/Institut Balseiro - Bariloche) Aristide Lemaitre (LPN – Marcoussis) Emmannuel Péronne - INSP Shuo Zhang - INSP

Phonons in nanostructures and low-dimensional structures • Ultrafast acoustics • Coherent phonons • Micro and nano acoustics • MEMS and NEMS (micro and nano electromechanical systems) • Phonons in devices for electronics, optoelectronics and spintronics • Electron-phonon interaction • Micro and nanoscale phonon heat transfer • Nanoscale energy conversion and thermo-electricity • Phonon transport • Solitons and nonlinear phenomena • Acoustic waves in anisotropic media and phonon imaging • Phonons in superconductors and magnetic materials • Phononic crystals • Surface and Interface phonons • Quantum fluids • Lattice dynamics • Phonons in glasses and disordered systems • Phase transitions • Light, neutron and X-ray inelastic scattering • New techniques • Particle detectors July 15–20, 2007 12th international conference on phonon scattering in condensed matter

UNIVERSITE Pierre & Marie CURIE