Interference effects in the Coulomb blockade regime: Current blocking and spin preparation in symmetric nanojunctions

Abstract

We consider nanojunctions in the single-electron tunneling regime which, due to a high degree of spatial symmetry, have a degenerate many-body spectrum. 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 to give necessary and sufficient conditions for interference blockade also in the presence of spin-polarized leads. As an example we analyze a triple quantum-dot single-electron transistor. For a setup with parallel polarized leads, we show how to selectively prepare the system in each of the three states of an excited spin triplet without application of any external magnetic field.

Subgap features due to quasiparticle tunneling in quantum dots coupled to superconducting leads

“…Spin degeneracies can be neglected in the presence of unpolarized or collinearly polarized leads. 30,39 Orbital degeneracies are system dependent and they are not present in the single and double quantum dot systems discussed in this paper. A detailed discussion of their effects can be found, for example, in Refs.…”

Topographical fingerprints of many-body interference in STM junctions on thin insulating films

“…In a recent publication we predicted the occurrence of NDC due to interference blocking [21][22][23] in an STM single benzene junction on a thin insulating film. 32 Benzene, however, is not easily accessible in STM experiments and it is not obvious to what extent the findings of Ref.…”

“…13 Last but not least, vibrational-mediated NDC has also been observed in single-molecule devices 14 and proposed to test position-dependent Franck-Condon factors in suspended carbon nanotubes. 15 Recently also interference phenomena in single-molecule junctions have attracted intense theoretical [16][17][18][19][20][21][22][23][24][25][26][27] and experimental [28][29][30][31] investigations. These junctions allow us to tackle the fundamental question of the quantum mechanical nature of the electronic transport at the nanoscale and exhibit dramatic modulations of the current desirable for applications.…”

Photon assisted long-range tunneling

“…In transport through quantum dots, longrange coupling has found interest for the prediction of the interference of spin superexchange trajectories 34 , the generation of entangled currents 35 , or the influence of dephasing 36 . It is also involved in the occurrence of dark states [37][38][39][40][41] .…”