Valence fluctuations and empty-state resonance for Fe adatom on a surface

TL;DR

This paper investigates the electronic resonance of Fe adatoms on Pt(111) surfaces, revealing valence fluctuations as the origin, and confirms findings with STM experiments, offering new insights into surface nanosystem behaviors.

Contribution

It introduces a combined first-principles and finite-temperature exact diagonalization approach to explain the empty-state resonance in Fe adatoms, improving upon previous theoretical models.

Findings

Resonance caused by valence fluctuations between impurity configurations

Theoretical results align with STM measurements

Paramagnetic state of impurity naturally reproduced

Abstract

We report on the formation of the high-energy empty-state resonance in the electronic spectrum of the iron adatom on the Pt(111) surface. By using the combination of the first-principles methods and the finite-temperature exact diagonalization approach, we show that the resonance is the result of the valence fluctuations between atomic configurations of the impurity. Our theoretical finding is fully confirmed by the results of the scanning tunneling microscopy measurements [M.F. Crommie et al., Phys. Rev. B 48, 2851 (1993)]. In contrast to the previous theoretical results obtained by using local spin density approximation, the paramagnetic state of the impurity in the experiment is naturally reproduced within our approach. This opens a new way for interpretation of STM data collected earlier for metallic surface nanosystems with iron impurities.