Inelastic Electron Tunneling Spectroscopy of a Mn Dimer

Abstract

A scanning tunneling microscope can probe the inelastic spin excitations of single magnetic atoms in a surface via spin-ip assisted tunneling. A particular and intriguing case is the Mn dimer case. We show here that the existing theories for inelastic transport spectroscopy do not explain the observed spin transitions when both atoms are equally coupled to the scanning tunneling microscope tip and the substrate, the most likely experimental situation. The hyperne coupling to the nuclear spins is shown to lead to a nite excitation amplitude, but the physical mechanism leading to the large inelastic signal observed is still unknown. We discuss some other alternatives that break the symmetry of the system and allow for larger excitation probabilities.

RKKY oscillations in the spin relaxation rates of atomic-scale nanomagnets

“…The previous discussion solves a formerly identified puzzle [28,51] in the interpretation of existing experiments of antiferromagnetically coupled Mn dimers on Cu 2 N [13,26]. Although we have centered our discussion of the spin dimer on the S = case, relevant for the Mn dimer.…”

“…In the ideal situation in which the tip is coupled to only one atom, there is no possible destructive interference and a clear step is expected. When the tip is right in the middle of the two atoms, a theory ignoring the phase difference between surface single-particle states scattering with the two atoms would predict a vanishing transition rate [51]. In contrast, such a modulation has not been observed experimentally.…”

“…As we discuss in detail below, this is far from being the case in experiments [26]. Therefore, the phase factors have to be included, a well known point [33,34,37,38,40] missed in recent papers dealing with Kondo interactions with short spin chains [28,31,45,51,52]. .…”