Nanoseminar in Physics 

IN-PERSON EVENT, REGISTER HERE to attend

Speaker: Prof. Stefan Dilhaire, University of Bordeaux, France

Abstract:  The reduction of the size of nano-objects or nano-materials down to the nanoscale leads to strong modifications of its transport properties depending then on its size, shape, structure and obviously on its environment. Carrier confinement combined to interface effects gives rise to new transport properties. That is the case in absorption and emission of light where the new properties are given by electromagnetic near field coupling between the nano-objets included in the material. Concerning phonon transport, a frequency dependence of thermal conductivity can be observed. Plasmons confined in a tapered wave guide slow down producing hot carriers. These hot electron life time increases in a hot spot. All these processes occurring at time scales from femtoseconds up to nanoseconds are routinely accessible with ultrafast pump-probe techniques. i.e heterodyne optical sampling allows to access to the energy transfer and understand the heat propagation into nano-objects themselves. The comprehension of energy transport mechanisms had been initiated by the study of a collection of nano-objects in solution without any coupling between them.

We will describe two situations where the energy deposited by a femtosecond flash can be converted into phonons which does not adopt a diffusive behavior or into plasmons making heat traveling at the speed of light. These phenomena are observed thanks to an ultrafast imaging technique revealing « exotic » propagation of heat at 20 Tera image per second. 

Hosted by Prof. Klaas-Jan Tielrooij, Ultrafast Dynamics in Nanoscale Systems Group Leader at ICN2

Introductory Talk: Hugo Gomez, Doctoral Student at  Ultrafast Dynamics in Nanoscale Systems:" Measurement of thermal conductivity of nanostructured materials using four-probe thermal conductivity method with AC measurements."