Electronic orders in multiorbital Hubbard models with lifted orbital degeneracy

Shintaro Hoshino and Philipp Werner
Phys. Rev. B 93, 155161 – Published 27 April 2016

Abstract

We study the symmetry-broken phases in two- and three-orbital Hubbard models with lifted orbital degeneracy using dynamical mean-field theory. On the technical level, we explain how symmetry relations can be exploited to measure the four-point correlation functions needed for the calculation of the lattice susceptibilities. In the half-filled two-orbital model with crystal-field splitting, we find an instability of the metallic phase to spin-orbital order with neither spin nor orbital moment. This ordered phase is shown to be related to the recently discovered fluctuating-moment induced spin-triplet superconducting state in the orbitally degenerate model with shifted chemical potential. In the three-orbital case, we consider the effect of a crystal-field splitting on the spin-triplet superconducting state in the model with positive Hund coupling, and the spin-singlet superconducting state in the case of negative Hund coupling. It is demonstrated that for certain crystal-field splittings the higher energy orbitals instead of the lower ones are relevant for superconductivity, and that Tc can be slightly enhanced by the crystal-field effect. We comment on the implications of our results for the superconductivity in strontium ruthenates, and for the recently reported light-enhanced superconducting state in alkali-metal-doped fullerides.

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  • Received 19 February 2016

DOI:https://doi.org/10.1103/PhysRevB.93.155161

©2016 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Shintaro Hoshino1 and Philipp Werner2

  • 1Department of Basic Science, The University of Tokyo, Meguro, Tokyo 153-8902, Japan
  • 2Department of Physics, University of Fribourg, 1700 Fribourg, Switzerland

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Issue

Vol. 93, Iss. 15 — 15 April 2016

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