ENERGY-DISTRIBUTION FUNCTION OF QUASI-PARTICLES IN MESOSCOPIC WIRES

We have measured with a tunnel probe the energy distribution function of Landau quasiparticles in metallic diffusive wires connected to two reservoir electrodes, with an applied bias voltage. The distribution f unction in the middle of a 1.5-mu m-long wire resembles the half sum o f the Fermi distributions of the reservoirs. The distribution function s in 5-mu m-long wires are more rounded, due to interactions between q uasiparticles during the longer diffusion time across the wire. From t he scaling of the data with the bias voltage, we find that the scatter ing rate between two quasiparticles varies as epsilon(-2), where epsil on is the energy transferred.