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Unconventional pairing and electronic dimerization instabilities in the doped Kitaev-Heisenberg model

Daniel D. Scherer, Michael M. Scherer, Giniyat Khaliullin, Carsten Honerkamp, and Bernd Rosenow
Phys. Rev. B 90, 045135 – Published 28 July 2014

Abstract

We study the quantum many-body instabilities of the tJKJH Kitaev-Heisenberg Hamiltonian on the honeycomb lattice as a minimal model for a doped spin-orbit Mott insulator. This spin-1/2 model is believed to describe the magnetic properties of the layered transition-metal oxide Na2IrO3. We determine the ground state of the system with finite charge-carrier density from the functional renormalization group (fRG) for correlated fermionic systems. To this end, we derive fRG flow equations adapted to the lack of full spin-rotational invariance in the fermionic interactions, here represented by the highly frustrated and anisotropic Kitaev exchange term. Additionally employing a set of the Ward identities for the Kitaev-Heisenberg model, the numerical solution of the flow equations suggests a rich phase diagram emerging upon doping charge carriers into the ground-state manifold (Z2 quantum spin liquids and magnetically ordered phases). We corroborate superconducting triplet p-wave instabilities driven by ferromagnetic exchange and various singlet pairing phases. For filling δ>1/4, the p-wave pairing gives rise to a topological state with protected Majorana edge modes. For antiferromagnetic Kitaev and ferromagnetic Heisenberg exchanges, we obtain bond-order instabilities at van Hove filling supported by nesting and density-of-states enhancement, yielding dimerization patterns of the electronic degrees of freedom on the honeycomb lattice. Further, our flow equations are applicable to a wider class of model Hamiltonians.

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  • Received 1 May 2014
  • Revised 30 June 2014

DOI:https://doi.org/10.1103/PhysRevB.90.045135

©2014 American Physical Society

Authors & Affiliations

Daniel D. Scherer1,*, Michael M. Scherer2, Giniyat Khaliullin3, Carsten Honerkamp4, and Bernd Rosenow1,5

  • 1Institut für Theoretische Physik, Universität Leipzig, D-04103 Leipzig, Germany
  • 2Institut für Theoretische Physik, Universität Heidelberg, D-69120 Heidelberg, Germany
  • 3Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany
  • 4Institute for Theoretical Solid State Physics, RWTH Aachen University, D-52056 Aachen, Germany and JARA - FIT Fundamentals of Future Information Technology, Germany
  • 5Physics Department, Harvard University, Cambridge, Massachusetts 02138, USA

  • *daniel.scherer@physik.uni-leipzig.de

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Issue

Vol. 90, Iss. 4 — 15 July 2014

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