Kagome antiferromagnet: A Schwinger-boson mean-field theory study

The Heisenberg antiferromagnet on the kagome lattice is studied in the framework of Schwinger-boson mean-field theory. Two solutions with different symmetries are presented. One solution gives a conventional quantum state with q=0 order for all spin values. Another gives a gapped spin liquid state for spin S=1/2 and a mixed state with both q=0 and √3×√3 orders for spin S>1/2. We emphasize that the mixed state exhibits two sets of peaks in the static spin structure factor. For the case of spin S=1/2, the gap value we obtained is consistent with the previous numerical calculations by other means. We also discuss the thermodynamic quantities such as the specific heat and magnetic susceptibility at low temperatures and show that our result is in a good agreement with the Mermin-Wagner theorem.