Weak localization in thin films

The resistance of two-dimensional electron systems such as thin disordered films shows deviations from Boltzmann theory, which are caused by quantum corrections and are called “weak localization”. Theoretically weak localization is originated by the Langer-Neal graph in the Kubo formalism. In this review article the physics of weak localization is discussed. It represents an interference experiment with conduction electrons spl into pairs of waves interfering in the back-scattering direction. The intensity of the interference (integrated over the time) can be easily measured b the resistance of the film. A magnetic field introduces a magnetic phase shift in the electronic wave functionand suppresses the interference after a “flight” time proportional to 1/H. Therefore the application of a magnetic field allows a time-of-flight experiment with conduction electrons. Spin-orbit scattering rotates the spin of the electrons and yields an observable destructive interference. Magnetic impurities destroy the coherence of the phase. The experimental results as well as the theory is reviewed. The role of the spin-orbit scattering and the magnetic scattering are discussed. The measurements give selected information about the inelastic lifetime of the conduction electrons in disordered metals and raise new questions in solid state physics. Future applications of the method of weak localization are considered and expected.