Temperature dependence of conductance of a tunnel junction coupled to a nanomechanical oscillator

Abstract

We have analyzed the electric current through a tunnel junction having its transition matrix elements modulated by a vibrational motion, with arbitrary voltage applied to the junction and arbitrary temperature of electrons in leads. This modulation can be realized by the introduction of molecules embedded between the leads, or by coupling the tunnel junction to a mechanical oscillator (cantilever). We find that the nonlinear current through this nanoelectromechanical system is proportional to the exponent of the ratio of the nonequilibrium dispersion of fluctuations of oscillator position and the tunneling length. An explicit expression for this dispersion of fluctuations is determined here on a microscopic basis, with its voltage and temperature dependencies. We have shown that for appropriate parameter values (oscillator mass and characteristic frequency, as well as the applied voltage bias) the conductance of the tunnel junction exhibits strong (almost exponential) dependence on temperature, which is in agreement with recent experimental data.