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TT: Fachverband Tiefe Temperaturen

TT 17: Poster Session: Correlated Electrons 1

TT 17.19: Poster

Montag, 1. April 2019, 15:00–18:30, Poster D

Quantum skyrmions in a triangular frustrated ferromagnet — •Vivek Lohani¹, Ciarán Hickey¹, and Achim Rosch^{1, 2} — ¹Institute of Theoretical Physics, University of Cologne, Germany — ²Department of Physics, Harvard University, Cambridge MA 02138, USA

Magnetic skyrmions are magnetization textures characterized by a topological winding number, initially discovered in chiral magnets. More recently, they were also predicted by Leonov and Mostovoy in a spin-1/2 Heisenberg ferromagnet with frustrated next-nearest neighbor interactions and spin-anisotropy. Their classical model predicts energetically degenerate skyrmions and antiskyrmions, and the emergence of a new zero mode, the helicity, reflecting rotation of spins around the z axis. The size of these frustration-stabilized skyrmions is also expected to be lesser than the ones found in chiral magnets. As a result, quantum properties of skyrmions might be of interest in insulating magnets at temperatures well below the bulk gap.

We investigate the existence of frustration-stabilized quantum skyrmions within a 31 site flake on a triangular lattice through exact diagonalization. We also derive the selection rules for the skyrmions in such a system. Next, we introduce a phenomenological Hamiltonian for mobile skyrmions and study couplings of the internal modes to the lowest order. This is then extended to an analysis of tunneling between skyrmions and antiskyrmions, and how the bandstructure is modified by the presence of tunneling terms, and its dependence on the number of flipped spins comprising the skyrmion.