Low Temperature Physics: 40, 73 (2014); https://doi.org/10.1063/1.4850536
Физика Низких Температур: Том 40, Выпуск 1 (Январь 2014), c. 92-104
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Mean-field RVB ground states of lattice models of CuNCNA.L. Tchougréeff and R. Dronskowski Institut für Anorganische Chemie RWTH-Aachen University, Landoltweg 1, D-52056, Aachen, Germany Received July 22, 2013 Аннотация Recently we proposed to describe the fascinating physics of copper carbodiimide, CuNCN, with help of the anisotropic trangular antiferromagnetic Heisenberg model with the parameters J_{a} and J_{ab} extending along the a, and a ± b lattice directions and a new frustrated Heisenberg antiferromagnetic model with exchange parameters J_{c}, J_{a}, and J_{ac}, extending along the c, a, and a ± c (c-a-ca model) directions assuming the resonating valence bond (RVB) type of the corresponding phases. Here we discuss possible RVB ground states of these models in the mean-field approximation and show that in either case it is a two-dimensional RVB state. The difference between the models is that in the ground state of the triangular model the quasiparticle spectrum features a finite (although exponentially small) energy gap for arbitrary weak Jab whereas that of the c-a-ca model shows two pseudogaps and a linear dependence of the quasiparticle density of states in the low-energy range. PACS: 75.10.Jm Quantized spin models, including quantum spin frustration; Ключевые слова: copper carbodiimide, crystal structure, spin liquid, resonating valence bond theory. |