Saw attenuation by the localised states of a 2D carrier system in a magnetic field

摘要

The surface acoustic wave attenuation and dispersion have been measrued as a function of magnetic field for both a 2D electron system and a 2D hole system at frequencies between 100 and 1100 MHz. The experiments were made at 350 mK in the quantum Hall regime. In the region of filling factor one where the quasi-DC conductivity becomes very small, an attenuation and dispersion is found which we attirbute to localised carrier states. We estimate that the relaxation time of the localised electrons is about 60 ps while the relaxation time for localised holes is about 20 ps.