21 research outputs found
Negative conductivity and anomalous screening in two-dimensional electron systems subjected to microwave radiation
A 2D electron system in a quantized magnetic field can be driven by microwave
radiation into a non-equilibrium state with strong magnetooscillations of the
dissipative conductivity. We demonstrate that in such system a negative
conductivity can coexist with a positive diffusion coefficient. In a finite
system, 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 non-equilibrium 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. Further, for a non-zero 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.Comment: 8 pages, 4 figure
Nonequilibrium phenomena in high Landau levels
Developments in the physics of 2D electron systems during the last decade
have revealed a new class of nonequilibrium phenomena in the presence of a
moderately strong magnetic field. The hallmark of these phenomena is
magnetoresistance oscillations generated by the external forces that drive the
electron system out of equilibrium. The rich set of dramatic phenomena of this
kind, discovered in high mobility semiconductor nanostructures, includes, in
particular, microwave radiation-induced resistance oscillations and
zero-resistance states, as well as Hall field-induced resistance oscillations
and associated zero-differential resistance states. We review the experimental
manifestations of these phenomena and the unified theoretical framework for
describing them in terms of a quantum kinetic equation. The survey contains
also a thorough discussion of the magnetotransport properties of 2D electrons
in the linear response regime, as well as an outlook on future directions,
including related nonequilibrium phenomena in other 2D electron systems.Comment: 60 pages, 41 figure