Jeudi 18 avril 2013 à 10h15
Salle 234, Ecole de Physique

Fractional Josephson Effect in a Quadruple Quantum Dot

Björn Sothmann, Université de Genève

The possibility to generate Majorana fermions in condensed-matter systems has recently generated a lot of excitement [1]. Apart from proposals based on nanowires, setups relying on double quantum dots have been suggested lately [2]. In these systems, the Majorana fermions lead to characteristic signatures in the zero-bias conductance. Here, we demonstrate the possibility to observe a fractional Josephson effect in two such double dots tunnel-coupled to each other. In contrast to a conductance measurement, the detection of Josephson currents does not require to couple additional leads to the quantum dots. Thereby, it offers a noninvasive way to probe Majorana physics. We discuss the robustness of the fractional Josephson effect with respect to perturbations away from a special point in parameter space. Finally, we address the limit of strongly coupled quantum dots. [1] J. Alicea, Rep. Prog. Phys. 75, 076501 (2012). [2] M. Leijnse and K. Flensberg, Phys. Rev. B 86, 134528 (2012).