COMBINED BLOCH AND SINGLE-ELECTRON-TUNNELING OSCILLATIONS IN ONE-DIMENSIONAL ARRAYS OF SMALL TUNNEL-JUNCTIONS

It is shown that at sufficiently low temperatures, one-dimensional arr ays of ultrasmall tunnel junctions (for example, semiconductor superla ttices) may exhibit an unusual type of electron transfer. This process can be considered as fast ''Bloch'' oscillations with frequency f(B) = epsilon/h (where epsilon is the electron energy change due to tunnel ing through one tunnel barrier), modulated with lower single-electron- tunneling frequency f(S) = I/e (where I is the dc electric current thr ough the array).