Orbital memory from individual Fe atoms on black phosphorus

Bistable valency in individual atoms presents an approach toward single-atom memory, as well as a building block to create tunable and stochastic multiwell energy landscapes. Yet, this concept of orbital memory has thus far only been observed for cobalt atoms on the surface of black phosphorus, which are switched using tipinduced ionization. Here, we show that individual iron atoms on the surface of black phosphorus exhibit orbital memory using a combination of scanning tunneling microscopy and spectroscopy with ab initio calculations based on density functional theory. Unlike cobalt, the iron orbital memory can be switched in its nonionized ground state. Based on calculations, we confirm that each iron valency has a distinct magnetic moment that is characterized by a distinguishable charge distribution due to the different orbital population. By studying the stochastic switching of the valency with varying tunneling conditions, we propose that the switching mechanism is based on a two-electron tunneling process.

Automated summary

This study demonstrates the orbital memory ability of individual iron atoms on the surface of black phosphorus and discovers that the iron orbital memory can be switched in its non-ionized ground state. By studying the variation of tunneling conditions, a two-electron tunneling process is proposed as the switching mechanism of the valency of iron atoms.