paper

Quantum phase diagram of Heisenberg antiferromagnet in honeycomb lattice: a modified spin wave study

arXiv:1603.08896 · doi:10.1088/0953-8984/28/40/406001

Abstract

Using modified spin wave (MSW) method, we study the Heisenberg model with first and second neighbor antiferromagnetic exchange interactions. For symmetric model, with the same couplings for all the equivalent neighbors, we find three phase in terms of frustration parameter : (1) a commensurate collinear ordering with staggered magnetization (N{é}el.I state) for , (2) a magnetically gapped disordered state for , preserving all the symmetries of the Hamiltonian and lattice, hence by definition is a quantum spin liquid (QSL) state and (3) a commensurate collinear ordering in which two out of three nearest neighbor magnetizations are antiparallel and the remaining pair are parallel (N{é}el.II state), for . We also explore the phase diagram of distorted model with . Distortion is introduced as an inequality of one nearest neighbor coupling with the other two. This yields a richer phase diagram by the appearance of a new gapped QSL, a gapless QSL and also a valence bond crystal (VBC) phase in addition to the previously three phases found for undistorted model.

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