Vibrational sidebands and dissipative tunneling in molecular transistors
Abstract
Transport through molecular devices with strong coupling to a single vibration mode is considered in the case where the vibration is damped by coupling to the environment. We consider the weak tunneling limit where a rate equation approach is valid. The role of the environment can be characterized the quality factor, Q, of the oscillator. For large values of Q the transport is governed by tunneling between displaced oscillator states giving rise to the well-known series of the Frank-Condon steps, while at small Q there is a cross over to a classical regime with an energy gap given by the classical displacement energy. The cross-over happens when Q=1/g, where g is the Frank-Condon coupling constant. Near the threshold voltage the current is a power law in voltage, with the power given by 2g/Q\pi.Keywords
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