Abstract
We present the theoretical study of weak localization in a disordered sandwich structure, which consists of a thin, dirty metallic film bounded by nearly insulating materials with electrical current primarily located in the metallic film. The conductance correction, δG(B), due to backscattering interference is calculated within the weak-localization theory as a function of perpendicular magnetic field B. It is found that, for a certain range of structural/material parameters, both the conductance correction δG(B = 0) and magnetoconductance (MC) show a weak temperature dependence (i.e. saturation) over a range of low temperatures, as opposed to those of a freestanding metallic film, which show a strong temperature dependence. At further lowered temperatures, it shows that δG(B = 0) and MC may or may not diverge, depending on the structure. If the structure is thin like a film, δG(B = 0) and MC both eventually diverge. On the other hand, if the structure is thick like a bulk, saturation of δG(B = 0) persists to 0K but MC is likely to diverge. We also fit the calculated MC of sandwich structures with the weak-localization theory suitable for a freestanding film, with the phase breaking time τ φ in the theory being the fitting parameter. This gives a nominal phase breaking time τ φ (eff) , which is nearly constant over a range of low temperatures. The implication of the work is discussed in connection with the issue of dephasing time saturation. The limitation of the present theory is examined and directions for future extension are suggested. © 2008 IOP Publishing Ltd.