Example：10.1021/acsami.1c06204 or Chem. Rev., 2007, 107, 2411-2502
XY magnetism, Kitaev exchange, and long-range frustration in theJeff=12honeycomb cobaltates Physical Review B (IF4.036), Pub Date : 2021-10-22, DOI: 10.1103/physrevb.104.134425 Shreya Das, Sreekar Voleti, Tanusri Saha-Dasgupta, Arun Paramekanti
The quest for Kitaev quantum spin liquids has led to great interest in honeycomb quantum magnets with strong spin-orbit coupling. It has been recently proposed that even Mott insulators with transition-metal ions, having nominally weak spin-orbit coupling, can realize such exotic physics. Motivated by this, we study the rhombohedral honeycomb cobaltates , and , using ab initio density-functional theory, which takes into account realistic crystal-field distortions and chemical information, in conjunction with exact diagonalization numerics. We show that these magnets host local moments with highly anisotropic factors, and we extract their full spin Hamiltonians including longer-range and anisotropic exchange couplings. For , we find a nearest-neighbor easy-plane ferromagnetic model with additional bond-dependent anisotropies and interlayer exchange, which supports three-dimensional Dirac nodal line magnons. In contrast, for and , we find a strongly suppressed interlayer coupling, and significant frustration from additional third-neighbor antiferromagnetic exchange mediated by P or As. Such bond-anisotropic spin models can support collinear zigzag or coplanar spiral ground states. We discuss their dynamical spin correlations which reveal a gapped Goldstone mode and argue that the effective parameters of the pseudospin- models in these two materials may be strongly renormalized by coupling to a low-energy spin exciton. Our results call for reexamining proposals for realizing Kitaev spin liquids in the honeycomb cobaltates.