Nonlinear resonant tunneling through doubly degenerate local state and strong electron-phonon interaction

In an approach of low transparency of the barrier the tunneling of electron s through doubly degenerate local state has been considered with allowance for the Coulomb and electron-phonon interactions. It is shown that in the c ase of weak electron-phonon and strong electron-electron interactions the d ependence of tunneling current on the applied voltage has a step-like chara cter at low temperature. The threshold value of the current was measured fo r small applied bias. The bistable state of the tunneling current is possib le in the region of large bias. In the case of strong electron-phonon and w eak electron-electron interactions, the threshold of tunneling current can be bistable. This result is a direct consequence of the electron pairing in local states. (C) 1999 American Institute of Physics. [S1063- 777X(99)0061 0-6].