Relativistic Band-Structure Calculations for CeTIn₅(T = Ir and Co) and Analysis of the Energy Bands by Using Tight-Binding Method

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 4 f 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 .