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O: Fachverband Oberflächenphysik

O 59: Spins on Surfaces at the Atomic Scale I

O 59.9: Vortrag

Mittwoch, 19. März 2025, 12:30–12:45, H6

Second harmonic driving of paramagnetic resonance of molecular spin through non-linear transport phenomena — •Stepan Kovarik¹, Richard Schlitz¹, Jose Reina-Gálvez^2,3, Aishwarya Vishwakarma¹, Dominic Ruckert¹, Nicolas Lorente^4,5, Christoph Wolf^2,3, Pietro Gambardella¹, and Sebastian Stepanow¹ — ¹ETH Zurich, Switzerland — ²QNS, Seoul, Korea — ³Ewha Woman University, Seoul, Korea — ⁴CFM, Donostia-San Sebastian, Spain — ⁵DIPC, Donostia-San Sebastian, Spain

The second harmonic excitation of electron paramagnetic resonance (EPR) originates from nonlinear processes. In this talk, I will demonstrate the presence of second and higher harmonic driving of a single spin in a pentacene molecule on 2ML MgO on Ag(001) when applying a radio-frequency electric field in an STM. Comparing our results to a theory considering EPR driven by a periodic modulation of the tunneling barrier [1] yields qualitative agreement, indicating the presence of higher harmonic driving. The key observation is that the barrier modulation can introduce nonlinearities to the electronic transport, leading to the excitation of magnetic resonance at the driving frequency [2] and at its multiples. Our work enhances the capabilities of EPR measurements in STM by introducing the frequency upconversion mechanism, showcasing the key role of electronic transport in driving the EPR. The presented findings apply also to other quantum transport systems, where the electrons are transported through discrete energy levels. References: [1]J. Reina-Gálvez et al., Phys. Rev. B 107, 235404 (2023)., [2]S. Kovarik et al., Science 384, 1368-1373 (2024).

Keywords: Magnetic resonance; Spin torque; Nonlinear phenomena; ESR-STM