SHORT-RANGE IMPURITY IN A MAGNETIC-FIELD - THE CONDUCTANCE OF A NARROW CHANNEL

We consider a single short-range impurity in a two-dimensional electro n-gas channel in a magnetic field. The conductance g of the channel wi th impurity is calculated in terms of the Green's function of the chan nel without impurity and the impurity scattering length. It is found t hat a series of downward dips in the graph of g versus Fermi energy E exist due to quasibound states with wave functions localized near the impurity. In a strong magnetic field such states exist also for a repu lsive impurity and not only below the band bottom of each transverse m ode, but also above it.