Electron paramagnetic resonance of alkali metal atoms and dimers on ultrathin MgO

Abstract

Electron paramagnetic resonance (EPR) can provide 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. Here, we demonstrate that EPR in combination with scanning tunneling microscopy (STM) allows for probing the bonding and charge state of alkali metal atoms on an ultrathin magnesium oxide layer on a Ag substrate. We observe a magnetic moment of $1{\mu }_{\mathrm{B}}$ for Li${}_2$, LiNa, and Na${}_2$ dimers corresponding to spin radicals with a charge state of $+1e$. Single alkali atoms have the same charge state and no magnetic moment. The ionization of the adsorbates is attributed to charge transfer through the oxide to the metal substrate. Our work highlights the potential of EPR-STM to provide insight into dopant atoms that are relevant for the control of the electrical properties of surfaces and nanodevices.

18 pages, 5 figures

References in corpus (5)

• Engineering the eigenstates of coupled spin-1/2 atoms on a surface
• Donor spins in silicon for quantum technologies
• Longitudinal and transverse electron paramagnetic resonance in a scanning tunneling microscope
• Excitation of local magnetic moments by tunnelling electrons
• Quantifying the interplay between fine structure and geometry of an individual molecule on a surface

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