Regensburg 2022 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 47: Focus Session: Atomic-Scale Studies of Spins on Surfaces with Scanning Tunneling Microscopy 1

O 47.5: Vortrag

Mittwoch, 7. September 2022, 16:15–16:30, S051

Electron Paramagnetic Resonance of individual Alkali Metal Atoms and Dimers on Ultrathin MgO — •Stepan Kovarik¹, Roberto Robles², Richard Schlitz¹, Tom Sebastian Seifert^1,3, Nicolas Lorente^2,4, Pietro Gambardella¹, and Sebastian Stepanow¹ — ¹Department of Materials, ETH Zurich, Switzerland — ²Centro de Física de Materiales, San Sebastian, Spain — ³Department of Physics, FU Berlin, Germany — ⁴Donostia International Physics Center, San Sebastian, Spain

Electron paramagnetic resonance (EPR) provides unique insight into the chemical structure and magnetic properties of dopants in oxide and semiconducting materials that are of interest for applications in electronics, catalysis, and quantum sensing. We demonstrate that EPR in combination with scanning tunneling microscopy (STM) [1, 2] allows for probing the spin and charge state of alkali metal atoms on an ultrathin magnesium oxide layer on a Ag(100) substrate. We identify a magnetic moment of 1 µ_B for Li₂, LiNa, and Na₂ dimers corresponding to spin radicals with a charge state of +1e [3]. Individual alkali atoms have the same charge state and no magnetic moment. The ionization of the adsorbates is attributed to the charge transfer of one electron through the oxide to the metal substrate. Our work highlights the potential of EPR-STM to provide insight into dopant atoms, which are relevant for the control of the electrical properties of surfaces and represent a suitable platform for studying quantum nanomagnets.

[1] S. Baumann et al., Science 350 (2015) [2] T. S. Seifert et al., PRR 2 (2020) [3] S. Kovarik et al., Nano Lett. 22 (2022)