Regensburg 2025 – scientific programme
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O: Fachverband Oberflächenphysik
O 90: Spins on Surfaces at the Atomic Scale II
O 90.5: Talk
Thursday, March 20, 2025, 16:00–16:15, H11
Switching Dynamics in Fe Spin Chains: Quantum vs. Classical Behavior — •Henrik Lichtl1, Lukas Veldman1, Johannes Schust1, Nicolaj Betz1,2, Laëtitia Farinacci1,3, Susanne Baumann1, and Sebastian Loth1,2 — 1University of Stuttgart, Institute for Functional Matter and Quantum Technologies, Stuttgart, Germany — 2Center for Integrated Quantum Science and Technology (IQST), University of Stuttgart, Stuttgart, Germany — 3Carl-Zeiss-Stiftung Center for Quantum Photonics Jena - Stuttgart - Ulm, Germany
That quantum spins transition to classical magnets at a certain size is well-known, but the behavior of magnets at this transition point has remained elusive. Here we develop a method to measure high speed magnetization curves in a scanning tunneling microscope (STM) that reach magnetic field sweep rates up to kT/s. This allows us to measure the magnetization reversal of antiferromagnetic few-atom spin chains, constructed of Fe atoms on a Cu2N surface. By resolving the statistics of the quantum jumps between the antiferromagnetic ground states, we can clearly distinguish between classical and quantum regimes of magnetic switching. Quantum mechanical behavior quenches rapidly with increasing size such that chains of more than five atoms in length can behave as classical magnets. The ability to modulate spin systems at high speed brings techniques that were previously reserved for bulk measurements to the atomic scale and provides deep insights into the coupling mechanisms between quantum spins and their environment.
Keywords: Scanning tunneling microscopy; Nano magnetism; Spins on surfaces