Thermal Mechanism of Absolute Negative Conductivity in Two-Dimensional Electron Systems

We calculate the dissipative dc conductivity of a two-dimensional electron system in a magnetic field for the situation when its effective temperature exceeds the temperature of the acoustic phonon system. We demonstrate that at sufficiently large difference between the electron and lattice temperatures (sufficiently strong microwave radiation) the dissipative dc conductivity can become negative. As an illustration, the case of the electron heating by microwave radiation is considered.