Topological superconductivity in the extended Kitaev-Heisenberg model

Abstract

We study superconducting pairing in the doped Kitaev-Heisenberg model by taking into account the recently proposed symmetric off-diagonal exchange $\Gamma$. By performing a mean-field analysis, we classify all possible superconducting phases in terms of symmetry, explicitly taking into account effects of spin-orbit coupling. Solving the resulting gap equations self-consistently, we map out a phase diagram that involves several topologically nontrivial states. For $\Gamma <0$, we find a competition between a time-reversal symmetry breaking chiral phase with Chern number $\pm 1$ and a time-reversal symmetric nematic phase that breaks the rotational symmetry of the lattice. On the other hand, for $\Gamma \ge 0$ we find a time-reversal symmetric phase that preserves all the lattice symmetries, thus yielding clearly distinguishable experimental signatures for all superconducting phases. Both of the time-reversal symmetric phases display a transition to a ${\mathbb{Z}}_2$ non-trivial phase at high doping levels. Finally, we also include a symmetry-allowed spin-orbit coupling kinetic energy and show that it destroys a tentative symmetry protected topological order at lower doping levels. However, it can be used to tune the time-reversal symmetric phases into a ${\mathbb{Z}}_2$ non-trivial phase even at lower doping.

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Cited by in corpus (5)

• Disorder-robust phase crystal in high-temperature superconductors stabilized by strong correlations
• Hydrated lithium intercalation into the Kitaev spin liquid candidate material $\alpha -$RuCl${}_3$
• Pairing tendencies in the doped Kitaev-Heisenberg model
• Possible Realization of Kitaev Spin Liquids in van der Waals Heterostructures of $\alpha$-RuCl${}_3$ and Cr$X_3$ ($X$=Cl and I)
• Ground State Properties of the Doped Kitaev-Heisenberg Chain: Topological Superconducting and Mott Insulating Phases Driven by Magnetic Frustration