Eur. Phys. J. B (2016) 89: 67
https://doi.org/10.1140/epjb/e2016-60916-x

Regular Article

Partially resummed perturbation theory for multiple Andreev reflections in a short three-terminal Josephson junction

¹ CNRS, Institut NEEL, BP 166, 38042 Grenoble Cedex 9, France
² Université Grenoble-Alpes, Institut NEEL, BP 166, 38042 Grenoble Cedex 9, France
³ Laboratoire de Physique Théorique et des Hautes Energies, CNRS UMR 7589, Université Pierre et Marie Curie, Sorbonne Universités, 4 Place Jussieu, 75252 Paris Cedex 05, France

^a e-mail: regis.melin@neel.cnrs.fr

Received: 26 November 2015
Received in final form: 21 January 2016
Published online: 14 March 2016

Abstract

In a transparent three-terminal Josephson junction, modeling nonequilibrium transport is numerically challenging, owing to the interplay between multiple Andreev reflection (MAR) thresholds and multipair resonances in the pair current. An approximate method, coined as “partially resummed perturbation theory in the number of nonlocal Green’s functions”, is presented that can be operational on a standard computer and demonstrates compatibility with results existing in the literature. In a linear structure made of two neighboring interfaces (with intermediate transparency) connected by a central superconductor, tunneling through each of the interfaces separately is taken into account to all orders. On the contrary, nonlocal processes connecting the two interfaces are accounted for at the lowest relevant order. This yields logarithmically divergent contributions at the gap edges, which are sufficient as a semi-quantitative description. The method is able to describe the current in the full two-dimensional voltage range, including commensurate as well as incommensurate values. The results found for the multipair (for instance quartet) current-phase characteristics as well as the MAR thresholds are compatible with previous results. At intermediate transparency, the multipair critical current is much larger than the background MAR current, which supports an experimental observation of the quartet and multipair resonances. The paper provides a proof of principle for addressing in the future the interplay between quasiparticles and multipairs in four-terminal structures.