科研之友
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摘要
A two-dimensional electron system in a quantizing magnetic field can be driven by microwave radiation into a nonequilibrium state with strong magneto-oscillations of the dissipative conductivity. We demonstrate that in such a system a negative conductivity can coexist with a positive diffusion coefficient. In a finite system, the solution of coupled electrostatic and linear transport problems shows that the diffusion can stabilize a state with negative conductivity. Specifically, this happens when the system size is smaller than the absolute value of the nonequilibrium screening length that diverges at the point where the conductivity changes sign. We predict that a negative resistance can be measured in such a state. Furthermore, for a nonzero difference between the work functions of two contacts, we explore the distribution of the electrostatic potential and of the electron density in the sample. We show that in the diffusion-stabilized regime of negative conductivity the system splits into two regions with opposite directions of electric field. This effect is a precursor of the domain structure that has been predicted to emerge spontaneously in the microwave-induced zero-resistance states.
- 出版日期2011-9-29
