Berlin 2024 – scientific programme
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O: Fachverband Oberflächenphysik
O 21: Focus Session: Spins on Surfaces studied by Atomic Scale Spectroscopies III
O 21.1: Topical Talk
Tuesday, March 19, 2024, 10:30–11:00, MA 004
Theory of Electron Spin Resonance in Scanning Tunneling Microscopy — •Juan Carlos Cuevas1, Christian R. Ast2, Piotr Kot2, Maneesha Ismail2, Sebastián de-la-Pena1, and Antonio I. Fernandez-Dominguez1 — 1Departamento de Fisica Teorica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autonoma de Madrid, 28049 Madrid, Spain — 2Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569 Stuttgart, Germany
Electron spin resonance (ESR) spectroscopy in scanning tunneling microscopy (STM) has enabled probing the electronic structure of single magnetic atoms and molecules on surfaces with unprecedented energy resolution. Despite this remarkable success, the field could still greatly benefit from a more quantitative understanding of the ESR-STM physical mechanisms. Here, we present a theory of ESR-STM which quantitatively models not only the ESR signal itself, but also the full background tunneling current, from which the ESR signal is derived. We show that this theory is able to quantitatively reproduce the experimental results for a spin 1/2 system (TiH molecules on MgO) across many orders of magnitude in tunneling current, providing access to the relaxation and decoherence rates that govern the spin dynamics due to intrinsic mechanisms and to the bias voltage. More importantly, and with the help of additional electromagnetic simulations, our work establishes that the transitions in our ESR-STM experiments can be driven by the ac magnetic field at the junction.
Keywords: ESR; STM; Green's functions; Quantum master equations