Crossover from nematic to magnetic low-temperature ground state in Fe(Se,Te) compounds

TL;DR

This study compares FeSe${}_{1-x}$Te${}_{x}$ and pure FeSe crystals, revealing a transition from nematic to magnetic ground states linked to changes in crystal structure and electronic energy levels.

Contribution

It provides new insights into how Te substitution alters the ground state from nematic to magnetic in FeSe-based compounds.

Findings

Anomaly in R(T) differs between FeSe and FeSe${}_{0.6}$Te${}_{0.4}$.

Change in ground state type from nematic to magnetic.

Alteration of energy level positions within the $t_{2g}$ multiplet explains the transition.

Abstract

A comparative analysis of the properties of FeSe${}_{1-x}$Te${}_{x}$ crystals in the range of x values of about 0.4 and pure FeSe crystals is presented. We found that the anomaly in R (T) at the structural transition for the former differs significantly from the corresponding anomaly for the latter. This indicates a change in the type of the ground state in the studied compounds. Within the framework of the crystal field model, this can be explained as a consequence of a change in the distortion of the tetrahedral environment of iron, which leads to a change in the positions of the energy levels within $t_{2g}$ multiplet. Depending on the mutual position of the degenerate xz and yz levels and the xy level, the type of transition can change from orbital ordering to magnetic ordering.