Electron Spin Resonance and Magnetic Resonance Imaging of the Delocalized Electron in a Lanthanide Atomic Wire

Electron spin resonance (ESR) of single atoms and organic molecules has been studied at the atomic scale using scanning probe microscopy techniques (SPM) which couple radio frequency to the tunneling junction. However, it remains to be demonstrated whether arbitrary electron systems delocalized in extended quantum dots can be addressed this way. Here we show that the spin resonance of an electron in a particle-in-a-box-like state confined to a 1-dimensional metallic lanthanide wire can be driven and sensed with the tip of a scanning tunneling microscope. We acquire spin resonance signals which vary dramatically depending on the position of the tip relative to the delocalized electron in the wire. We also observe novel features in magnetic resonance images which do not map directly to the electron spin density. Further, we observe magnetic properties that arise from the unique interplay between the localized 4f electrons and the delocalized wire electron. Our results establish the generality of ESR-SPM to address delocalized electron systems and provide opportunities to realize exciting new physics which arises from localized spins in lanthanide atoms embedded in nanostructures.