NEGATIVE ELECTRON DRAG AND HOLE-LIKE BEHAVIOR IN THE INTEGER QUANTUM HALL REGIME

Electron drag between two two-dimensional electron gases in magnetic f ields has been observed with a polarity opposite to that for zero fiel d. This negative drag requires that the electrons have a holelike disp ersion. Density dependence measurements in the integer quantum Hall re gime show that the drag is negative only when the upper Landau level o f one layer is more than half filled while the other is less than half filled, indicating that holelike dispersion is present in one-half of each Landau level. Negative drag is argued to be a consequence of dis order. [S0031-9007(98)07296-2].