NEW MICROWAVE INDUCED RESONANCES IN THE CONDUCTANCE OF A GaAs/Ga//1// minus //xAl//xAs HETEROJUNCTION.

Abstract

We have observed microwave induced resonances in the conductance of a GaAs/Ga//1// minus //xAl//xAs heterojunction placed in a uniform magnetic field and cooled to 1. 7K. In addition to the narrow spin resonance and the broad oscillations due to microwave heating reported by Stein et al, we observed a new series of resonances for given conditions. This series consists of two resonances per Landau level and is observed already at microwave powers one to two orders of magnitude lower than the minimum required to see the microwave heating signal. We believe these new resonances to result from non-resonant spin transitions within each Landau level. It is the underlying Landau level structure which converts these non-resonant transitions into resonant changes in conductance. As a result we have a sensitive probe of the Landau level density of states.