Asymmetric Coulomb blockade and Kondo temperature of single-molecule transistors

Abstract

Recent experiments on single-molecule transistors made of cobalt complexes exhibited anomalously weak gate voltage dependence of the Kondo temperature accompanied by a strong asymmetry in the Coulomb blockade peaks. We show that these observations can both be explained by strong electron–vibron interactions when including anharmonicities of the molecular potential surfaces. The strong electron–vibron interactions may originate from a tendency of the cobalt complexes toward Jahn–Teller distortion.