Interplay of magnetic order and Jahn-Teller distortion in a model with strongly correlated electron system

TL;DR

This paper investigates how magnetic order influences Jahn-Teller distortion in a strongly correlated electron system modeled by a two-fold degenerate Hubbard model, revealing coexistence conditions and temperature effects.

Contribution

It introduces a combined model incorporating magnetic order and Jahn-Teller interaction, analyzing their interplay in correlated electron systems.

Findings

Magnetic order and Jahn-Teller distortion coexist at low temperatures for certain parameters.

Distortion appears only when Jahn-Teller coupling exceeds a critical value.

Temperature affects lattice strain and magnetization near the critical Jahn-Teller coupling.

Abstract

The Hubbard model has been employed successfully to understand many aspects of correlation driven physical properties, in particular, the magnetic order in itenerant electron systems. In some systems such as Heusler alloys, manganites etc., it is known that, in addition to magnetic order, distortion induced by Jahn-Teller(J-T) effect also exists. In this paper, based on two-fold degenerate Hubbard model, the influence of magnetic order on J-T distortion is investigated. The electron correlation is treated using a spectral density approach and J-T interaction is added to the model. We find that magnetic order and structural distortion coexist at low temperature $T$ for a certain range of electron correlation strength $U$, J-T coupling strength $G$ and band occupation $n$. At T=0, for a given $n$ and $U$, magnetic order is present but distortion appears only for a $G$ larger than a critical value. We also studied the temperature dependence of lattice strain and magnetization choosing a $G$ close to the critical value.