Electron-electron scatttering in Sn-doped indium oxide thick films

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We have measured the low-field magnetoresistances (MRs) of a series of Sn-doped indium oxide thick films in the temperature T range 4--35 K. The electron dephasing rate 1/τφ as a function of T for each film was extracted by comparing the MR data with the three-dimensional (3D) weak-localization theoretical predictions. We found that the extracted 1/τφ varies linearly with T³/². Furthermore, at a given T, 1/τφ varies linearly with kF⁻⁵/²l⁻³/², where kF is the Fermi wavenumber, and l is the electron elastic mean free path. These features are well explained in terms of the small-energy-transfer electron-electron scattering time in 3D disordered conductors. This electron dephasing mechanism dominates over the electron-phonon (e-ph) scattering process because the carrier concentrations in our films are 3 orders of magnitude lower than those in typical metals, which resulted in a greatly suppressed e-ph relaxation rate.