Tunable magnetic textures in spin valves: From spintronics to Majorana bound states

Spin-valve structures in which a change of magnetic configuration is responsible for magnetoresistance led to impressive advances in spintronics, focusing on magnetically storing and sensing information. However, this mature technology also offers versatile control of magnetic textures with usually neglected underlying fringing fields to enable entirely different applications by realizing topologically nontrivial states. Together with proximity-induced superconductivity in a two-dimensional electron gas with a large g factor, these fringing fields realized in commercially available spin valves provide Zeeman splitting, synthetic spin-orbit coupling, and confinement, needed for Majorana bound states (MBS). Detailed support for the existence and control of MBS is obtained by combining accurate micromagnetic simulation of fringing fields used as an input in the Bogoliubov-de Gennes equation to calculate low-energy spectrum, wave-function localization, and local charge neutrality. A generalized condition for a quantum phase transition in these structures provides valuable guidance for the MBS evolution and implementing reconfigurable effective topological wires.