Phase diagram and quantum order by disorder in the kitaev K1 - K2 honeycomb magnet

Ioannis Rousochatzakis, Johannes Reuther, Ronny Thomale, Stephan Rachel, N. B. Perkins

Research output: Contribution to journalArticlepeer-review

85 Scopus citations


We show that the topological Kitaev spin liquid on the honeycomb lattice is extremely fragile against the second-neighbor Kitaev coupling K2, which has recently been shown to be the dominant perturbation away from the nearest-neighbor model in iridate Na2IrO3, and may also play a role in α-RuCl3 and Li2IrO3. This coupling naturally explains the zigzag ordering (without introducing unrealistically large longer-range Heisenberg exchange terms) and the special entanglement between real and spin space observed recently in Na2IrO3. Moreover, the minimal K1 - K2 model that we present here holds the unique property that the classical and quantum phase diagrams and their respective order-by-disorder mechanisms are qualitatively different due to the fundamentally different symmetries of the classical and quantum counterparts.

Original languageEnglish (US)
Article number041035
JournalPhysical Review X
Issue number4
StatePublished - 2015


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