13 juin 2017

Café des Sciences PROMES-SOLSTICE le 14 juin, à 10h30, salle de conférences à Tecnosud par Vasily Temnov - Probing ultrafast heat transport in thin metallic bi-layer structures

14 juin 2017 à 10h30, Salle des conférences, PROMES/Tecnosud

Probing ultrafast heat transport in thin metallic bi-layer structures

Vasily Temnov
IMMM CNRS 6283, Université du Maine, 72085 Le Mans cedex, France
Groupe d’Etude de la Matière Condensée (GEMaC), CNRS UMR 8635,
Université de Versailles-Saint Quentin en Yvelines, Université Paris-Saclay

Hybrid metal-ferromagnet multilayer structures play an important role in nanophotonic applications [1,2]. Here we show how ultrafast pump-probe measurements on hybrid metal-ferromagnet bilayer structures helped to explore a new physical phenomenon: ultrafast transient overheating of ferromagnetic layer excited by hot electrons through a macroscopically thick layer of noble metal. Combined with numerical two-temperature model simulations of ultrafast heat diffusion, our experimental observations reveal the dominant role of the interfacial thermal boundary (Kapitza) resistance at metal-ferromagnet interfaces and different electron-phonon coupling strength between noble and ferromagnetic transition metals. Observation of exchange-coupled magnons by non-equilibrium hot electrons as well as the quantitative characterization of ultrashort acoustic pulses accomplishes the physical picture. The physics reported in this talk opens the door to novel pathways of femtosecond-laser material nanostructuring via deep sub-surface overheating of lattice at the nano-scale in complex solid multilayer structures.