Schwinger-Boson Approach to Quantum Spin Systems: Gaussian Fluctuations in the "Natural" Gauge

A. E. Trumper, L. O. Manuel, C. J. Gazza, H. A. Ceccatto
1997 Physical Review Letters  
We compute the Gaussian-fluctuation corrections to the saddle-point Schwinger-boson results using collective coordinate methods. Concrete application to investigate the frustrated J1-J2 antiferromagnet on the square lattice shows that, unlike the saddle-point predictions, there is a quantum nonmagnetic phase for 0.53 < J2/J1 < 0.64. This result is obtained by considering the corrections to the spin stiffness on large lattices and extrapolating to the thermodynamic limit, which avoids the
more » ... h avoids the infinite-lattice infrared divergencies associated to Bose condensation. The very good agreement of our results with exact numerical values on finite clusters lends support to the calculational scheme employed.
doi:10.1103/physrevlett.78.2216 fatcat:fjjv5rynfvd2voyldfh7wkwo5e