Valence bond spin liquid state in two-dimensional frustrated spin-1/2 Heisenberg antiferromagnets
Abstract
Fermionic valence bond approach in terms of SU(4) representation is proposed to describe the
J
1
−
J
2
frustrated Heisenberg antiferromagnetic (AF) model on a {\it bipartite} square lattice. A uniform mean field solution without breaking the translational and rotational symmetries describes a valence bond spin liquid state, interpolating the two different AF ordered states in the large
J
1
and large
J
2
limits, respectively. This novel spin liquid state is gapless with the vanishing density of states at the Fermi nodal points. Moreover, a sharp resonance peak in the dynamic structure factor is predicted for momenta
q=(0,0)
and
(π,π)
in the strongly frustrated limit
J
2
/
J
1
∼1/2
, which can be checked by neutron scattering experiment.