Relativistic Band-Structure Calculations for CeTIn$_5$(T=Ir and Co)

TL;DR

This study uses relativistic band-structure calculations to analyze the electronic properties of CeTIn$_5$ superconductors, constructing a simplified tight-binding model to better understand their complex energy bands and differences.

Contribution

The paper introduces a simplified tight-binding model based on relativistic band calculations to analyze CeTIn$_5$ compounds, highlighting the importance of crystalline electric field effects.

Findings

Fermi surfaces match experimental results from de Haas-van Alphen measurements.

Energy bands are complex, requiring simplified models for analysis.

Differences between CeIrIn$_5$ and CeCoIn$_5$ are linked to crystalline electric field effects.

Abstract

In order to investigate electronic properties of recently discovered heavy fermion superconductors CeTIn$_5$ (T=Ir and Co), we employ the relativistic linear augmented-plane-wave (RLAPW) method to clarify the energy band structures and Fermi surfaces of those materials. The obtained energy bands mainly due to the large hybridization between Ce $4f$ and In 5$p$ states well reproduce the Fermi surfaces consistent with the de Haas-van Alphen experimental results. However, when we attempt to understand magnetism and superconductivity in CeTIn$_5$ from the microscopic viewpoint, the energy bands obtained in the RLAPW method are too complicated to analyze the system by further including electron correlations. Thus, it is necessary to prepare a more simplified model, keeping correctly the essential characters of the energy bands obtained in the band-structure calculation. For the purpose, we construct a tight-binding model for CeTIn$_5$ by including $f$-$f$ and $p$-$p$ hoppings as well as $f$-$p$ hybridization, which are expressed by the Slater-Koster integrals, determined by the direct comparison with the band-calculation result. Similarity and difference between CeIrIn$_5$ and CeCoIn$_5$ are discussed based on the obtained tight-binding model, suggesting a significant importance of the effect of crystalline electric field to understand the difference in electronic properties among CeTIn$_5$.