2011/08/31 by Subhro Bhattacharjee, Sung-Sik Lee, Yong Baek Kim · 2 citations
Physics and Astronomy · #Advanced Condensed Matter Physics #Anisotropy #Coupling (piping) #Ground state #Hamiltonian (control theory) #Lattice (music) #Magnetic field #Magnetic moment #Physics of Superconductivity and Magnetism #Topological Materials and Phenomena #Trigonal crystal system #cond-mat.str-el
paper · pdf · doi:10.1088/1367-2630/14/7/073015
published as New J. Phys. 14, 073015 (2012) · 13 pages (Draft expanded; references updated; typos corrected and discussion on recent experiments added)
arxiv created 2012/05/10 · openalex publication_date 2012/07/06 · arxiv updated 2012/07/10 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The nature of the effective spin Hamiltonian and magnetic order in the honeycomb iridates is explored by considering a trigonal crystal field effect and spin–orbit (SO) coupling. Starting from a Hubbard model, an effective spin Hamiltonian is derived in terms of an emergent pseudo-spin-1/2 moment in the limit of large trigonal distortions and SO coupling. The present pseudo-spins arise from a spin–orbital locking and are different from the j eff = 1/2 moments that are obtained when the SO coupling dominates and trigonal distortions are neglected. The resulting spin Hamiltonian is anisotropic and frustrated by further neighbour interactions. Mean-field theory suggests a ground state with four-sublattice zigzag magnetic order in a parameter regime that can be relevant to the honeycomb iridate compound Na 2 IrO 3 , where a similar magnetic ground state has recently been observed. Various properties of the phase, the spin-wave spectrum and experimental consequences are discussed. The present approach contrasts with the recent proposals to understand iridate compounds starting from the strong SO coupling limit and neglecting non-cubic lattice distortions.