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The Kitaev-Heisenberg (KH) model describes the transition between a spin liquid
and an antiferromagnet, it is expected to be realized in iridates on the
honeycomb lattice [1]. Viewing the Kitaev spin model as a Mott insulator at
half filling, we investigate the competing interactions away from that limit by
applying a slave boson theory. Contrary to the Heisenberg interaction, the
Kitaev interaction favors topologically interesting p-wave superconductivity,
which in the doped regime is robust against the admixture of a Heisenberg
coupling [2]. While the symmetry of the superconducting order is equivalent to the B-phase of Helium-3 for symmetric exchange couplings and in the absence of a Zeeman field, we find different types of order in the presence of a Zeeman field and with asymmetric exchange couplings. Additional insights into the nature of the superconducting state are provided by the quasi-particle spectrum and the magnetic susceptibiltiy of an isolated impurity, which we study in the T-matrix approach. [1] G. Jackeli and G. Khaliullin, Phys. Rev. Lett. 102, 017205 (2009). [2] T. Hyart, A.R. Wright, G. Khaliullin and B. Rosenow, preprint arXiv:1109.6681 (2011). |
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