Quantum Interference Effect in a Periodic System in the Ballistic Region

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Current-orientation dependence of bulk residual resistivity, negative bend resistance and nonlinear I-V characteristics have been observed in ultrahigh-purity aluminium single crystals at 4.2K.In this project, further, quantum oscillations due to magnetic breakdown in the transverse magnetoresistance have been measured on single crystals of ultrahigh-purity aluminium at 4.2K.In a specimen with the [110] current direction, monotonically increasing oscillations superimposed on the linear increase of magnetoresistivity are observed in magnetic fields up to B = 4.0 T directed in the [001] crystallographic orientation. On the other hand, in a specimen with the [100], current direction, the bottom and the top of the oscillations and their amplitude have been found to increase stepwise every three cycles with increasing magnetic fields, while the amplitude increases monotonically among three cycles. For this current direction, also a sudden increase and decrease in the period DELTA (1/B) of the oscillations against 1/B have been observed around the mean value of 2.15 * 10^<-2> T^<-1> every six cycles. It is suggested that these stepwise changes of the oscillations arises from a new quantum interference effect of electron waves.