Magneto-Rotons and Transport in the Fractional Quantum Hall Effect

The fractional quantum Hall effect is a remarkable macroscopic quantum phenomenon occurring in the two-dimensional electron gas (inversion layer) at high magnetic fields and low temperatures. The Hall resistivity is found to be accurately quantized in the form rho sub (xy) = h/e sup 2 nu where nu is a simple rational fraction. Associated with and of central importance to this quantization of rho sub (xy) is the appearance of exponentially small dissipation rho sub (xx) - exp (-DELTA/T) due to the finite excitation gap DELTA. Great progress has recently been made in understanding the nature of the correlated ground state, which at least for filling factors of the form nu = 1/m appears to be well described by Laughlin's variational wave function[1].