Quantum phase transition in the frustrated Heisenberg antiferromagnet

Abstract

Using the ${\mathit{J}}_{1\mathrm{\ensuremath{-}}}$${\mathit{J}}_{2}$ model, we present a description of quantum phase transition from N\'eel ordered to the spin-liquid state based on the modified spin-wave theory. The general expression for the gap in the spectrum in the spin-liquid phase is given.