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Kitaev-Heisenberg Model on a Honeycomb Lattice: Possible Exotic Phases in Iridium Oxides A 2 IrO 3

2010; American Physical Society; Volume: 105; Issue: 2 Linguagem: Inglês

10.1103/physrevlett.105.027204

1092-0145

Jiří Chaloupka, George Jackeli, Giniyat Khaliullin,

Magnetic and transport properties of perovskites and related materials

We derive and study a spin one-half Hamiltonian on a honeycomb lattice describing the exchange interactions between ${\mathrm{Ir}}^{4+}$ ions in a family of layered iridates ${A}_{2}{\mathrm{IrO}}_{3}$ ($A=\mathrm{Li},\mathrm{Na}$). Depending on the microscopic parameters, the Hamiltonian interpolates between the Heisenberg and exactly solvable Kitaev models. Exact diagonalization and a complementary spin-wave analysis reveal the presence of an extended spin-liquid phase near the Kitaev limit and a conventional N\'eel state close to the Heisenberg limit. The two phases are separated by an unusual stripy antiferromagnetic state, which is the exact ground state of the model at the midpoint between two limits.