Transverse magnetoresistance of the two-dimensional chiral metal

We consider the two-dimensional chiral metal, which exists at the surface o f a layered, three-dimensional sample exhibiting the integer quantum Hall e ffect. We calculate its magnetoresistance in response to a component of mag netic field perpendicular to the sample surface, in the low temperature, bu t macroscopic, regime where inelastic scattering may be neglected. The magn etoresistance is positive, following a Drude form with a field scale B-0 = Phi(0)/al(el) given by the transverse field strength at which one quantum o f flux Phi(0) passes through a rectangle with sides set by the layer-spacin g a and the elastic mean free path l(el). Experimental measurement of this magnetoresistance may, therefore, provide a direct determination of the ela stic mean free path in the chiral metal. [S0163-1829(99)05807-5].