Self-assembly of magnetic Co atoms on stanene

Abstract

We have investigated magnetic Co atoms self-assembled on ultraflat stanene on Cu(111) substrate by utilizing scanning tunneling microscopy/spectroscopy (STM/STS) in conjunction with density functional theory (DFT). By means of depositing Co onto the stanene/Cu(111) held at 80 K, Co atoms have developed into monomer, dimer, and trimer structures containing one, two, and three Co atoms, respectively. As per atomically resolved topographic images and bias-dependent apparent heights, the atomic structure models based on Sn atoms substituted by Co atoms have been deduced, which are in agreement with both self-consistent DFT calculations and STM simulations. Apart from that, the projected density of states has revealed a maximum at around $\ensuremath{-}0.5$ eV from the Co-3${d}_{3{z}^{2}\ensuremath{-}{r}^{2}}$ minority band, which contributes predominately to the peak feature at about $\ensuremath{-}0.3$ eV in tunneling conductance $(dI/dU)$ spectra taken at the Co atomic sites. As a result of the exchange splitting between the $\mathrm{Co}\text{\ensuremath{-}}3d$ majority and minority bands, there are nonzero magnetic moments, including about $0.60{\ensuremath{\mu}}_{B}$ in monomer, $0.56{\ensuremath{\mu}}_{B}$ in dimer, and $0.29{\ensuremath{\mu}}_{B}$ in trimer of the Co-atom assembly on the stanene. Such a magnetic Co-atom assembly, therefore, could provide the vital building blocks to stabilize the local magnetism on two-dimensional stanene with nontrivial topological properties.