Abnormal positive magnetoresistance in a weak magnetic field in Ge on the metallic side close to the metal–insulator transition at low temperatures

Abstract

We observed an abnormal positive magnetoresistance in Ge doped with Arsenic, a the non-magnetic impurity at relatively small magnetic fields and low temperatures (below 100 mK) which was very different to the positive magnetoresistance connected with the wave-function shrinkage effect, obtained at higher temperatures and magnetic fields. The abnormal positive magnetoresistance was saturated in magnetic fields in a range of 0.4–0.6 T. We consider that the resistivity of our system is influenced by the scattering of electrons on superconducting fluctuations, like the Maki–Thomson correction. In a small magnetic field, these fluctuations are suppressed, resulting in an abnormal positive magnetoresistance.