Event Details

Hybrid Topological Nanodevices for quantum technologies

Topological hybrid system have been recently proposed a novel platform for the field of the quantum technologies. Hereafter we discuss two different theoretical but realistic proposals we have developed @ NEST.

Firstly we will concentrate on the idea to create and manipulate Majorana fermions in a 2DEG Josephson junctions(see Fig.1)[1]. We will show how controlling the Josephson phase difference a non-trivial phase with Majorana fermions can be induced in the Josephson channel proximised with ferromagnetic superconductors (such as Al/EuS films). We will show how the Majorana fermions can be manipulated, such as moved along the junction, keeping the topological protection and using only dissipationless current controls.

In the second part we will discuss how we can manipulate the entanglement symmetry in a hybrid topological Josephson junction. In particular we will investigate the supercurrent in a hybrid topological Josephson junction done with two superposed layer of topological insulator (see Fig.2) which allows local (LAR) and crossed (CAR) Andreev reflections with the s-wave leads[2]. Applying realistic external potentials, such as gate voltages or magnetic flux, to the junction one can uniquely affect the non-local and local component of the dissipationless current. In particular gate voltages are able to change the spin symmetry of non-local Cooper pairs from singlet to triplet. We discuss notable limits demonstrating that entanglement symmetry is manipulated and that can be identified in the critical current measurement. We examine the universal behaviour of the critical current, how it depends on the amplitude ratio between the CAR and LAR processes.

[1] P. Virtanen, F. S. Bergeret, E. Strambini, F. Giazotto, A. Braggio“Majorana bound states hybrid 2D Josephson junctions” Phys. Rev. B 98,020501(R) (2018)

[2]G. Blasi, F. Taddei, V. Giovannetti, A. Braggio “Manipulation of Cooper pair entanglementin hybrid topological Josephson junctions” Phys. Rev. B 99, 064514 (2019)