Abstract: Lanthanide atoms are promising ingredients for realizing single molecule magnets which remain magnetically stable at elevated temperatures. They are also being explored for their use in quantum information processing due to the relatively long relaxation times and phase coherence times of their magnetic 4f-electrons and nuclear spins. These useful properties arise in part due to the strong localization of their 4f electrons, which are shielded from the surrounding environment by their much larger valence 6s and 5d electrons. Recently, Electron Spin Resonance combined with the Scanning Tunneling Microscope (ESR-STM) has been developed into a powerful tool to address individual atomic spins on surfaces, providing both atomic-scale spatial resolution and coherent control of spin states. However, driving and sensing spin resonance in lanthanide atoms with ESR-STM has remained a challenge due to the f-electron shielding, which inhibits magnetoresistive sensing required for the technique.
In today’s seminar, we’ll discuss our recent successful demonstration of electron spin resonance of individual lanthanide atoms using a scanning tunneling microscope. These atoms were bound to a protective insulating film and prepared in the monovalent state with an unpaired 6s electron, enabling tunnel current to access their 4f electrons via their magnetic valence shell. Europium spectra display a rich array of transitions among the 54 combined electron and nuclear spin states, which remarkably can all be accessed within a 10-30 GHz energy window due to both vanishing orbital angular momentum and minimal magnetic anisotropy. Monovalent europium is therefore promising as a model spin qudit system with a large Hilbert space. In marked contrast, monovalent samarium’s ground state is a simple Kramers doublet, but with an extraordinarily large and anisotropic g-factor close to 5. These results demonstrate that all-electronic sensing and control of individual lanthanide spins is possible for quantum devices and spin-based electronics by using their rarely-observed monovalent cation state.
See the paper on arXiv!