Sebastian Loth

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Magnetic atoms on surfaces provide a precisely controllable platform for studying spin dynamics across a wide range of regimes from individual quantum spins to nanoscale classical magnets. Using scanning tunneling microscopy (STM) combined with atomic force microscopy (AFM) at millikelvin temperatures, we investigate atomic-scale spin dynamics at the boundary between quantum and classical behavior.
Antiferromagnetic Fe spin chains on Cu₂N/Cu(100) serve as a model system to resolve the quantum-to-classical crossover in magnetization reversal. By driving fast magnetic field ramps at kT/s through avoided level crossings, we identify Landau-Zener dynamics in antiferromagnetic spin chains. Complementary measurements with magnetic exchange force microscopy on individual paramagnetic Fe atoms on MgO/Ag(100) give direct access to the forces exerted by a dynamically switching quantum spin on a macroscopic cantilever. This coupling between atomic spin dynamics and mechanical degrees of freedom ultimately enables a single-atom electric motor, in which current-induced spin switching drives free mechanical oscillations of the cantilever demonstrating direct conversion of quantum spin excitations into classical mechanical work with high efficiency.

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Universität Stuttgart
PH2
Contact: Thomas Michely / Matteo Cacco