New class of magnetoresistance oscillations: Interaction of a two-dimensional electron gas with leaky interface phonons

We report on a new class of magnetoresistance oscillations observed in a hi gh-mobility two-dimensional electron gas (2DEG) in GaAs-AlxGa1-xAs heterost ructures. Appearing in a weak magnetic held (B < 0.3 T) and only in a narro w temperature range (2 K < T < 9 K), these oscillations are periodic in 1/B with a frequency proportional to the electron Fermi wave vector, k(F). We interpret the effect as a magnetophonon resonance of the 2DEG with leaky in terface-acoustic phonon modes carrying a wave vector q = 2k(F). Calculation s show a few branches of such modes existing on the GaAs-AlxGa1-xAs interfa ce, and their velocities are in quantitative agreement with the observation .