We propose a magnetically disordered ground state for a frustrated quantum antiferromagnet. This disordered state is an array of spin singlets spontaneously formed on four spin plaquettes. Both perturbation results and bond-operator calculations show that this phase has lower energy than the columnar dimer state. Analysis of available numerical data on finite clusters also supports the conclusion that this state is realized at intermediate frustrations. © 1996 The American Physical Society.

• Received 18 June 1996

DOI:https://doi.org/10.1103/PhysRevB.54.9007