Transport in Molecular Junctions

Correlated single molecule junctions display a fascinating spectrum of different transport characteristics. We concentrate here on the signatures of the intrinsic electronic correlation and of the coupling to molecular vibrations. In these systems a crucial role is played by the contacts, which represent the interface between the molecule and the measuring circuit. A short review over nanogap realizations and anchoring methods opens the chapter. Particular attention is dedicated to scanning tunnelling microscopy, which naturally delivers atomic scale control on the contact geometry. Moreover, this technique allows for the simultaneous recording of spectroscopic and topographical information about the studied molecule. We show the importance of this complementary information with two examples: the non-equilibrium spin-crossover and the apparent orbital reversal, both manifestations of intrinsic electronic correlations. Vibrational effects are introduced with the help of the archetypal Anderson-Holstein model. The connection between microscopic parameters and transport characteristics is illustrated, with particular focus on the Franck-Condon blockade in molecular single electron transistors.