Four-terminal magnetoresistance of a two-dimensional electron-gas constriction in the ballistic regime

Abstract

A novel negative magnetoresistance effect is found in four-terminal measurements of the voltage drop across a short constriction of variable width in a high-mobility two-dimensional electron gas. The effect is interpreted as the suppression by a magnetic field of the geometrical constriction resistance in the ballistic regime. Quantitative agreement with a simple model based on a Landauer-type formula is obtained.