Ambipolar transition voltage spectroscopy: analytical results and experimental agreement

This work emphasizes that the transition voltages $V_{t \pm}$ for both bias polarities ($V${\raisebox{1.2ex}{$_{\stackrel{>}{<}}$}0}) should be used to properly determine the energy offset $\varepsilon_{0}$ of the molecular orbital closest to electrodes' Fermi level and the bias asymmetry $\gamma$ in molecular junctions. Accurate analytical formulas are deduced to estimate $\varepsilon_{0}$ and $\gamma$ solely in terms of $V_{t \pm}$. These estimates are validated against experiments, by showing that full experimental $I$-$V$-curves measured by Beebe et al [\prl 97, 026801 (2006)] and Tan et al [Appl. Phsy. Lett. 96, 013110 (2010)] for both bias polarities can be excellently reproduced.