Many bulk magnets and magnetic thin films exhibit helical or spin-spiral ground states. In the presence of magnetic field, spin spirals can transform to topologically protected whirling textures called magnetic skyrmions, while in nanowires deposited on top of superconductors Majorana bound states can be formed, both of which being prospective hardware elements of quantum information technology. Quantum mechanical (first principles) calculation of the electronic structure of spin-spiral states is possible via the generalized Bloch theorem in case of simultaneous translational and spin-rotational symmetry. Self-consistent calculation of the spin-spiral state is possible only in the non-relativistic limit, while effects of spin-orbit coupling can be accounted for by using perturbation techniques. The PhD student will aquire the use of the spin-spiral code developed in our research group in terms of the multiple scattering Green's-function formalism. As first application, we plan to determine the magnetic ground state of an Fe monolayer on top of Ta(110) for which both recent experiments and previous spin-model studies explored a rather long wave-length spin spiral. A particular goal of the PhD work is to extend the code to infinite on-dimensional wires and perform calculations for magnetic wires in connection to topological superconductivity as proposed in Fe wires on Re(0001) or Mn wires on Nb(110). In addition, we intend to combine this code with the solution of the Bogoliubov - de Gennes equations which will enable to study proximity-induced superconductivity in these systems.
Spin-spiral states in ultrathin films and nanowires
Fizikai Tudományok Doktori Iskola
thorough knowledge in relativistic quantummechanics, theoretical solid state physics and strong motivation for computational research
PhD project for standard admission