Electronic structure of atomic manganese chains supported on Cu$_2$N / Cu (100)

TL;DR

This study combines STM and DFT to uncover a localized, spin-polarized edge state at 1 eV above the Fermi level in Mn chains on Cu$_2$N/Cu(100), revealing complex electronic and magnetic interactions dependent on chain length.

Contribution

It provides the first detailed analysis of the electronic edge states and magnetic coupling in Mn chains supported on Cu$_2$N/Cu(100), highlighting the presence of a Tamm-like edge state and the effects of chain length parity.

Findings

Discovery of a localized, spin-polarized edge state at ~1 eV above Fermi energy.

Odd and even Mn chains exhibit different magnetic coupling behaviors.

Electronic structure at -1 eV is mainly spin unpolarized due to N p-states.

Abstract

Scanning tunnelling microscopy and density functional theory studies of manganese chains adsorbed on Cu$_2$N/Cu (100) reveal an unsuspected electronic edge state at $\sim 1$ eV above the Fermi energy. This Tamm-like state is strongly localised to the last Mn atom of the chain and fully spin polarised. However, no equivalence is found for occupied states, and the electronic structure at $\sim -1$ eV is mainly spin unpolarised due to the extended $p$-states of the N atoms that mediate the coupling between the Mn atoms in the chain. Odd-numbered Mn chains present an exponentially decreasing direct coupling with distance between the two edges, leading to a vanishing bonding/anti-bonding splitting of states while even-numbered Mn chains present perfect decoupling of both edges due to the the antiferromagnetic ordering of Mn chains.