Slow relaxation of magnetoresistance in doped p -GaAs/AlGaAs layers with partially filled upper Hubbard band

We observed slow relaxation of magnetoresistance in quantum well structures GaAs-AlGaAs with a selective doping of both wells and barrier regions which allowed partial filling of the upper Hubbard band. Such a behavior is explained as related to magnetic-field driven redistribution of the carriers between sites with different occupation numbers due to spin correlation on the doubly occupied centers. This redistribution, in its turn, leads to slow multi-particle relaxations in the Coulomb glass formed by the charged centers.Comment: 6 pages, 3 figure

Ionic conductivity on a wetting surface

Recent experiments measuring the electrical conductivity of DNA molecules highlight the need for a theoretical model of ion transport along a charged surface. Here we present a simple theory based on the idea of unbinding of ion pairs. The strong humidity dependence of conductivity is explained by the decrease in the electrostatic self-energy of a separated pair when a layer of water (with high dielectric constant) is adsorbed to the surface. We compare our prediction for conductivity to experiment, and discuss the limits of its applicability.Comment: 5 pages, 3 figures; one section and two illustrations added; figures updated and discussion added; typo fixe