|M.Sc Student||Danzig Almog|
|Subject||Observation of quantum (phonon) friction in hcp solid|
|Department||Department of Physics||Supervisor||Professor Emeritus Emil Polturak|
|Full Thesis text|
Quantum friction is a dissipative force resulting from exchange of quantized excitations between solid bodies moving relative to each other. One such quantum mechanism of friction involving phonons was predicted by Popov. Here, we present measurements of the friction force between crystallites of solid 4He contained inside a torsional oscillator. Our data are in excellent agreement with the temperature dependence predicted by the phonon friction model. This quantum friction force is many orders of magnitude weaker than classical friction at room temperature. To the best of our knowledge this is the first experimental observation of quantum friction.