Speaker: Panagiotis Kotetes (Niels Bohr Institute, University of Copenhagen, Denmark)
In this talk, I will elaborate on the interplay of magnetic textures and superconductivity, and its pivotal role for actualizing topological superconductors. Remarkably, magnetic textures allow engineering topological superconductivity without the requirement of spin-orbit coupling. I will first discuss the possibility of inducing topological superconductivity in an antiferromagnetic chain deposited on top of a conventional superconductor . This becomes possible via the combination of an external Zeeman field and the presence of a supercurrent flow through the superconducting substrate. The external fields effectively convert the antiferromagnetic ordering into a helical one. Further, I will consider systems in which magnetic textures are intrinsic and appear by virtue of interactions and Fermi surface nesting. Such a scenario can, for instance, take place in the iron pnictides, in which the coexistence of magnetism and superconductivity has been demonstrated experimentally, and a recent theoretical analysis  has revealed that magnetic textures are also accessible. Thus, I will focus on the arising topological superconducting phases in layered multiband materials with magnetic spiral, whirl or skyrmion order, coexisting with various types of spin-singlet superconductivity. The diverse magnetic phases lead to a variety of flat, unidirectional and chiral Majorana edge modes. One finds that this multifaceted manifestation of Majorana fermion modes stems from the interplay of topological phases with both gapped and nodal bulk energy spectra.
 A. Heimes, P. Kotetes and G. Schön, Phys. Rev. B 90, 060507(R) (2014).
Time: 14:00 pm, March 14 (Wed.), 2018
Venue: Rm N408, UCAS Zhong-Guan-Cun Teaching Building [Map]