INPLANE MAGNETIC-FIELD-INDUCED ANISOTROPY OF 2D FERMI CONTOURS AND THE FIELD-DEPENDENT CYCLOTRON MASS

The electronic structure of a 2D gas subjected to a tilted magnetic fi eld, with a strong component parallel to the GaAs/AlGaAs interface and a weak component oriented perpendicularly, is studied theoretically. It is shown that the parallel field component modifies the originally circular shape of a Fermi contour while the perpendicular component dr ives an electron by the Lorentz force along a Fermi line with a cyclot ron frequency given by its shape. The corresponding cyclotron effectiv e mass is calculated self-consistently for several concentrations of 2 D carriers as a function of the in-plane magnetic field. The possibili ty of detecting its field-induced deviations from the zero-field value experimentally is discussed.