Orbital memory from individual Fe atoms on black phosphorus

TL;DR

This study demonstrates that individual iron atoms on black phosphorus exhibit orbital memory that can be switched in their non-ionized ground state, revealing new possibilities for atomic-scale memory devices.

Contribution

It is the first to show orbital memory in iron atoms on black phosphorus and explains the switching mechanism as a two-electron tunneling process.

Findings

Iron atoms exhibit distinguishable valency states with unique magnetic moments.

Orbital memory can be switched without ionization, unlike cobalt.

Switching mechanism involves a two-electron tunneling process.

Abstract

Bistable valency in individual atoms presents a new approach toward single-atom memory, as well as a building block to create tunable and stochastic multi-well 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 tip-induced 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 non-ionized 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.