Interference single electron transistors based on quantum dot molecules Andrea Donarini and Milena Grifoni Abstract We consider nanojunctions in the single electron tunneling regime which, due to a high degree of spatial symmetry, have a degenerate many-body spec- trum. They comprise single molecule quantum dots as well as artificial quantum dot molecules. As a consequence, interference phenomena which cause a current blocking can occur at specific values of the bias and gate voltage. We present here a general formalism providing necessary and sufficient conditions for interference blockade also in the presence of spin-polarized leads. As examples we analyze a triple quantum dot as well as a benzene molecule single electron transistor. 1 Introduction Single particle interference is one of the most genuine quantum mechanical effects. Since the original double-slit experiment [1], it has been observed with electrons in vacuum [2, 3] and even with the more massive C 60 molecules [4]. Mesoscopic rings threaded by a magnetic flux provided the solid-state analogous [5, 6]. Intra- molecular interference has been recently discussed in molecular junctions for the case of strong [7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18] and weak [19, 20, 21] molecule-lead coupling. What unifies these realizations of quantum interference is that the travelling particle has two (or more) spatially equivalent paths at disposal to go from one point to another of the interferometer. Interference, though is hindered by decoherence. Generally, for junctions in the strong coupling regime decoherence can be neglected due to the short time Andrea Donarini Theoretische Physik, Universit¨ at Regensburg, 93040 Regensburg, Germany, e-mail: andrea.donarini@physik.uni-r.de Milena Grifoni Theoretische Physik, Universit¨ at Regensburg, 93040 Regensburg, Germany, e-mail: milena.grifoni@physik.uni-r.de 1