Low temperature properties of the triangular-lattice antiferromagnet: A bosonic spinon theory

Abstract

We study the low temperature properties of the triangular-lattice Heisenberg antiferromagnet with a mean field Schwinger spin- 1/2 boson scheme that reproduces quantitatively the zero temperature energy spectrum derived previously using series expansions. By analyzing the spin-spin and the boson density-density dynamical structure factors, we identify the unphysical spin excitations that come from the relaxation of the local constraint on bosons. This allows us to reconstruct a free energy based on the physical excitations only, whose predictions for entropy and uniform susceptibility seem to be reliable within the temperature range 0 ≤T ≲ 0.3J , which is difficult to access by other methods. The high values of entropy, also found in high temperature expansion studies, can be attributed to the roton-like narrowed dispersion at finite temperatures. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.