Excitation of spin waves by tunnelling electrons in one-dimensional ferro and anti-ferromagnets

TL;DR

This paper investigates how tunnelling electrons from an STM can excite spin waves in finite chains of magnetic atoms, revealing high excitation probabilities and differences between ferro- and antiferromagnetic couplings.

Contribution

It provides a detailed analysis of spin wave excitations in finite magnetic chains induced by tunnelling electrons, including energy spectra and the effects of magnetic coupling types.

Findings

High excitation probability of magnetic levels by tunnelling electrons

Similar excitation spectra across different chain lengths

Distinct behaviors in ferro- and antiferromagnetic chains, including entanglement effects

Abstract

Excitation of finite chains of magnetic atoms adsorbed on a surface by tunnelling electrons from an STM (Scanning Tunnelling Microscope) tip is studied using a Heisenberg Hamiltonian description of the magnetic couplings along the chain and a strong coupling approach of inelastic tunnelling. The excitation probability of the magnetic levels is very high and the excitation spectra in chains of different lengths are very similar. The excitations in finite chains can be considered as spin waves quantized in the finite object. The energy and momentum spectra of the spin waves excited in the idealized infinite chain by tunnelling electrons are determined from the results on the finite chains. Both ferro- and antiferromagnetic couplings are considered, leading to very different results. In particular, in the anti-ferromagnetic case, excitations linked to the entanglement of the chain ground state are evidenced.