Unconventional metamagnetic electron states in orbital band systems

TL;DR

This paper explores how orbital band structures in transition metal oxides lead to unconventional nematic electron states driven by Fermi surface instabilities and metamagnetism, with implications for materials like Sr$_3$Ru$_2$O$_7$.

Contribution

It extends Fermi surface instability analysis to orbital band systems, revealing how hybridization causes anisotropic distortions and nematic states induced by metamagnetism.

Findings

Band hybridization shifts Landau interactions to non-s-wave channels.

Nematic states can be induced by metamagnetic transitions.

Application to Sr$_3$Ru$_2$O$_7$ explains anisotropic high-field states.

Abstract

We extend the study of the Fermi surface instability of the Pomeranchuk type into systems with orbital band structures, which are common features in transition metal oxides. Band hybridization significantly shifts the spectra weight of the Landau interactions from the conventional s-wave channel to unconventional non-s-wave channels, which results in anisotropic (nematic) Fermi surface distortions even with ordinary interactions in solids. The Ginzburg-Landau free energy is constructed by coupling the charge-nematic, spin-nematic and ferromagnetic order parameters together, which shows that nematic electron states can be induced by metamagnetism. The connection between this mechanism to the anisotropic metamagnetc states observed in Sr$_3$Ru$_2$O$_7$ at high magnetic fields is studied in a multi-band Hubbard model with the hybridized quasi-one dimensional $d_{xz}$ and $d_{yz}$-bands.