Regensburg 2022 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 19: Topological Superconductors

TT 19.4: Vortrag

Mittwoch, 7. September 2022, 12:30–12:45, H23

Complex magnetic ground states and topological electronic phases of atomic spin chains on superconductors — •Jannis Neuhaus-Steinmetz¹, Elena Vedmedenko¹, Thore Posske², and Roland Wiesendanger¹ — ¹Department of Physics, University of Hamburg, 20355 Hamburg, Germany — ²I. Institute for Theoretical Physics, University of Hamburg, D-20355 Hamburg, Germany

Understanding the magnetic properties of atomic chains and nanoscopic wires on superconductors is an essential cornerstone on the road towards controlling and constructing topological matter. Yet, even in the simplest models of suspended chains, the classes of available magnetic ground states remain debated. Ferromagnetic (FM), antiferromagnetic (AFM), and spiral configurations have been suggested and experimentally detected, while additionally non-coplanar and complex collinear phases have been conjectured. Here, we resolve a recent controversy by determining the magnetic ground states of chains of magnetic atoms in proximity to a superconductor with Monte-Carlo methods, which employ the initial tight-binding model directly without further simplifications. We confirm the existence of FM, AFM and spiral ground states, and identify additional more complex ground states. We topologically classify the electronic structures, and investigate the stability of the magnetic states against increasing superconductivity. In addition, we introduce a computationally efficient alternative for approximating the magnetic ground state with an effective Heisenberg model, which we demonstrate by using our previous results as a benchmark for this new method.