摘要
We present a study of electric instability in a two-dimensional electron gas system under high magnetic fields. As the applied dc electric current exceeds a threshold value Ith, we find that the longitudinal magnetoresistance Rxx fluctuates and exhibits negative differential resistivity (NDR). The observed instability occurs only in well-separated low-lying Landau levels (LLs) with a filling factor ν≤2, and the onset of NDR can be described by the theory of Andreev et al. We find that Ith increases with increasing magnetic field B and the lattice temperature TL. In contrast, NDR becomes more pronounced at higher B, but gradually diminishes with increasing TL. Data analysis suggests that NDR is actuated by the suppression of Rxx with increasing electric field, which can be understood in terms of the capability of the spectral diffusion of electrons and of electron transfer to higher levels via inelastic inter-LLs scattering in the limit of one-occupied LL.