gamma-Mn at the border between weak and strong correlations

TL;DR

This study explores the magnetic fluctuation effects on gamma-Mn's spectral properties, revealing its position at the boundary between weak and strong electronic correlations, and emphasizing the importance of Hund's exchange parameter.

Contribution

It compares advanced and approximate computational methods to analyze gamma-Mn, highlighting the sensitivity of magnetic moment formation to Hund's exchange and the limitations of perturbative approaches.

Findings

Gamma-Mn exhibits strong correlation features like Hubbard bands.

Perturbative methods fail to capture the full spectral properties.

Small parameter changes can shift gamma-Mn between weak and strong correlation regimes.

Abstract

We investigate the role of magnetic fluctuations in the spectral properties of paramagnetic gamma-Mn. Two methods are employed. The Local Density Approximation plus Dynamical Mean-Field Theory together with the numerically exact quantum Monte-Carlo solver is used as a reference for the spectral properties. Then the same scheme is used with the computationally less demanding perturbative spin-polarized fluctuation-exchange solver in combination with the Disordered Local Moment approach, and photoemission spectra are calculated within the one-step model. It is shown that the formation of local magnetic moments in gamma-Mn is very sensitive to the value of Hund's exchange parameter. Comparison with the experimental photoemission spectra demonstrates that gamma-Mn is a strongly correlated system, with the Hubbard band formation, which cannot be described by the perturbative approach. However, minor change of parameters would transform it into a weakly correlated system.