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arXiv · 2008.13171

Hund physics landscape of two-orbital system

Siheon Ryee·Myung Joon Han·Sangkook Choi
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Abstract

Motivated by the recent discovery of superconductivity in infinite-layer nickelates RE$_{1-\delta}$Sr$_\delta$NiO$_2$ (RE$=$Nd, Pr), we study the role of Hund's coupling $J$ in a quarter-filled two-orbital Hubbard model which has been on the periphery of the attention. A region of negative effective Coulomb interaction of this model is revealed to be differentiated from three- and five-orbital models in their typical Hund's metal active fillings. We identify distinctive regimes including four different correlated metals, one of which stems from the proximity to a Mott insulator while the other three, which we call "intermediate" metal, weak Hund's metal, and valence-skipping metal, from the effect of $J$ being away from Mottness. Defining criteria characterizing these metals are suggested, establishing the existence of Hund's metallicity in two-orbital systems.

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Siheon Ryee, Myung Joon Han, Sangkook Choi. 2020-08-30. Hund physics landscape of two-orbital system. https://doi.org/10.1103/physrevlett.126.206401

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