Maximilian E. Merkel^1*, Claude Ederer^1*

1 Materials Theory, ETH Zürich, 8093 Zürich, Switzerland

* Corresponding authors emails: maximilian.merkel@mat.ethz.ch, claude.ederer@mat.ethz.ch

DOI10.24435/materialscloud:3s-b5 [version v1]

Publication date: Oct 29, 2021

How to cite this record

Maximilian E. Merkel, Claude Ederer, Charge disproportionation and Hund's insulating behavior in a five-orbital Hubbard model applicable to d^4 perovskites, Materials Cloud Archive 2021.184 (2021), doi: 10.24435/materialscloud:3s-b5.

Description

We explore the transition to a charge-disproportionated insulating phase in a five-orbital cubic tight-binding model applicable to transition-metal perovskites with a formal d^4 occupation of the transition-metal cation, such as ferrates or manganites. We use dynamical mean-field theory to obtain the phase diagram as a function of the average local Coulomb repulsion U and the Hund's coupling J. The main structure of the phase diagram follows from the zero band-width (atomic) limit and represents the competition between high-spin and low-spin homogeneous and an inhomogeneous charge-disproportionated state. This results in two distinct insulating phases: the standard homogeneous Mott insulator and the inhomogeneous charge-disproportionated insulator, recently also termed Hund's insulator. We characterize the unconventional nature of this Hund's insulating state. Our results are consistent with previous studies of two- and three-orbital models applicable to isolated t2g and eg subshells, respectively, with the added complexity of the low-spin/high-spin transition. We also test the applicability of an effective two-orbital (eg-only) model with disordered S=3/2 t2g core spins. Our results show that the overall features of the phase diagram in the high-spin region are well described by this simplified two-orbital model but also that the spectral features exhibit pronounced differences compared to the full five-orbital description.

Materials Cloud sections using this data

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File name	Size	Description
README.txt MD5md5:e7b45b65406066d6ab4a144204c8f828	3.7 KiB	Description of content of tight_binding.tar.gz and pythtb_to_Hk_file.py
tight_binding.tar.gz MD5md5:eaed503a6cf92ca6343444193777b59d	179.2 MiB	tar.gz archive with all data and scripts needed to generate TB models, run DMFT on them and post-process results
pythtb_to_Hk_file.py MD5md5:de5a8c724450f6f9f8917c2df7b7393f	5.0 KiB	Python script to generate the necessary files for the triqs H(k) converter from the pythTB model

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External references

Keywords

dynamical mean-field theory metal-insulator transition charge disproportionation MARVEL/DD5