Schwinger-boson approach to quantum spin systems: gaussian fluctuations in the natural gauge

TRUMPER, ADOLFO E.; L. O. MANUEL; GAZZA, CLAUDIO J.; CECCATTO, H. A.

PHYSICAL REVIEW LETTERS

American Physical Society

Lugar: New York; Año: 1997 vol. 78 p. 2216 - 2216

0031-9007

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 infinite-lattice infrared divergencies associated with Bose condensation. The very good agreement of our results with exact numerical values on finite clusters lends support to the calculational scheme employed.