Origin of the Quantum-Critical Transition in the Bilayer Heisenberg Model
Phys. Rev. Lett. 78, 3019 – Published 14 April, 1997
DOI: https://doi.org/10.1103/PhysRevLett.78.3019
Abstract
The bilayer Heisenberg antiferromagnet is known to exhibit a quantum-critical transition at a particular value of the interlayer coupling. Using a new type of coherent state, appropriate to the special order parameter structure of the bilayer, we map the problem onto the quantum nonlinear sigma model. It is found that the bare coupling constant diverges at the classical transition, so that in any finite dimension the actual transition occurs inside the ordered phase of the classical theory.