Anomalous transport due to retroreflection

Abstract

The magnetotransport of an electron gas in a two-dimensional, random arrangement of overlapping retroreflective crosses is studied using a combination of experiment and classical event-driven molecular dynamics simulation. The experimentally measured magnetoconductivity ${\ensuremath{\sigma}}_{xx}$ as a function of the magnetic field $B$ displays an anomalous behavior at low $B$ fields, accompanied with an increase of ${\ensuremath{\sigma}}_{xx}$ with increasing temperature at $B=0$. The simulations show that at $B=0$ the magnetoconductivity does not exist and is associated with anomalous diffusion in the asymptotic long-time limit that depends on the orientational order of the obstacles. At any finite $B$ field, the motion of the tracer particle is asymptotically diffusive but the diffusion coefficient vanishes with a power law in the limit $B\ensuremath{\rightarrow}0$.