NONCLASSICAL DISORDERED PHASE IN THE STRONG QUANTUM LIMIT OF FRUSTRATED ANTIFERROMAGNETS

The rotationally invariant Schwinger-boson approach to quantum helimagnets is discussed. It is shown that in order to get quantitative agreement with exact results on finite lattices, parity-breaking pairing of bosons must be allowed. For the J1-J2-J3 model on the special line J2 = 2J3, a quantum disordered phase is found, though notably only in the strong quantum limit S = 1/2. The theory predicts the direct melting of biaxial helimagnetic order into an isotropic spin fluid, without the formation of an intermediate spin-nematic phase as recently suggested.