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- $\frac {1}{2}$ 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 ≲ 0.3 J , 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.