Geometric resonance of bragg-reflected cyclotron orbits in unidirectional lateral superlattices: The role of harmonics of the potential modulation

A new class of small amplitude low-field magnetoresistance oscillation observed in a unidirectional lateral superlattice (ULSL) attributable to the geometric resonance of Bragg-reflected cyclotron orbits (open orbits) reveals the presence of higher harmonics in the potential modulation. By contrast, the commensurability oscillation (CO) exhibited by the same ULSL sample appears to be explicable by a formula taking only the fundamental component into consideration. The apparent inconsistency is ascribed to the difference in the sensitivity to the higher harmonics of the two types of magnetoresistance oscillations. The amplitude of the new oscillation is discussed in terms of the probability of the magnetic breakdown and the ratio of the distance traveled by the electrons during one period of the open orbit to the mean free path.