2005/01/17 by B. Reulet, Bertrand Reulet, D. E. Prober
Engineering · Physics and Astronomy · #Electromagnetic Compatibility and Noise Suppression #Microwave and Dielectric Measurement Techniques #Superconducting and THz Device Technology #cond-mat.mes-hall
paper · pdf · doi:10.1103/physrevlett.95.066602
4 pages, 2 figures
arxiv created 2005/01/17 · openalex publication_date 2005/08/02 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The current noise density S2 of a conductor in equilibrium, the Johnson noise, is determined by its temperature T: S2=4kBTG, with G the conductance. The sample's noise temperature TN=S2/(4kBG) generalizes T for a system out of equilibrium. We introduce the ``noise thermal impedance'' of a sample as the ratio \ensuremathδTN^\ensuremathω/\ensuremathδPJ^\ensuremathω of the amplitude \ensuremathδTN^\ensuremathω of the oscillation of TN when heated by an oscillating power \ensuremathδPJ^\ensuremathω at frequency \ensuremathω. For a macroscopic sample, it is the usual thermal impedance. We show for a diffusive wire how this (complex) frequency-dependent quantity gives access to the electron-phonon interaction time in a long wire and to the diffusion time in a shorter one, and how its real part may also give access to the electron-electron inelastic time. These times are not simply accessible from the frequency dependence of S2 itself.