The fractional quantum hall effect under hydrostatic pressure

Abstract

We report on experiments performed on a high quality, high carrier concentration Al x Ga 1−x As GaAs heterostructure at a range of hydrostatic pressures. At a pressure of 1 bar a clear ϱ xx minimum and Hall plateau were observed associated with a 5 3 fractional state while no such structure was observed for the 4 3 fractional state. At increasing pressure however structure in the resistivity components ϱ xx and ϱ xy for the 4 3 state became increasingly pronounced. As the disorder in the sample and the measured activation energy for the 5 3 state remained relatively unchanged with increasing pressure we speculate that the enhancement of the 4 3 state with increasing pressure is due to an increase in the energy gap for this state.