CPM Seminar

New platforms for 1D topological superconductors: spin polarization and transport properties

Pascal Simon

LPS Orsay

One-dimensional (1D) topological superconductors have drawn a lot of attention in recent years since they support Majorana edge states. many systems have been proposed to emulate 1D topological superconductors though most of the focus was upon semiconducting wires with a Zeeman and spin-orbit interaction in proximity of a s-wave superconductors. I will show that a 1D RKKY systems in proximity to an s-wave superconductor support a helical magnetic order and may therefore form another platform to observe Majorana fermions.

This applies at low enough temperature to a quantum wire in proximity of a superconductor when the hyperfine interaction between electrons and nuclear spins is taken into account [1] or to a chain of magnetic adatoms adsorbed on a superconducting surface[2].

In the second part of my talk, if time permits, I will introduce a new local quantity dubbed “Majorana polarization” and argue that it can be used as a local order parameter to characterize the topological transition between a trivial system and a system exhibiting Majorana bound modes. Using this mathematical tool, we have found that signatures of the Majorana fermions can be found in the transverse electron spin polarization, and we propose to test the presence of Majorana fermions in a 1D system by a spin-polarized density of states measurements [3]. I will then present recent results regarding the interplay between Majorana fermions and Andreev bound states in long SN and SNS junctions [4].

[1] B. Braunecker, P. Simon, D. Loss, Phys. Rev. B 80, 165119 (2009).
[2] B. Braunecker and P. Simon, Phys. Rev. Lett. 111, 147202 (2013).
[3] D. Sticlet, C. Bena, P. Simon, Phys. Rev. Lett. 108, 096802 (2012).
[4] D. Chevallier, D. Sticlet, P. Simon, C. Bena, Phys. Rev. B 85, 235307 (2012); ibid Phys. Rev. B 87, 165414 (2013).