EDGE MAGNETOPLASMONS ON A LIQUID-HELIUM SURFACE AND QUANTUM TRANSPORTIN A HIGH MAGNETIC-FIELD

We have measured the linewidth of edge magnetoplasmons (EMP) propagate d at the edge of surface state electrons on a liquid He-4 surface from 90 to 1400 mK and for magnetic fields up to 6.4 T. We have confirmed that sigma(zz) obtained from the linewidth at 1100 mK agrees with sigm a(zz) obtained from the capacitive measurement of Dykman et al. Below 700 mK, where the scattering by ripplons predominates the transport, w e have observed that sigma(zz) is inversely proportional to the square root of temperature and independent of magnetic field. The temperatur e dependence agrees with theories, while the absence of the magnetic f ield dependence does not.