Abstract
A consistent theory of the Heisenberg quantum antiferromagnet in the disordered phase with short-range antiferromagnetic order was developed on the basis of the path integral for the spin coherent states. We presented the Lagrangian of the theory in the form that is explicitly invariant under rotations and found natural variables in terms of which one can construct a perturbation theory. The short-wavelength spin fluctuations are similar to the ones in spin-wave theory, and the long-wavelength spin fluctuations are governed by the nonlinear sigma model. We also demonstrated that the short-wavelength spin fluctuations should be considered accurately in the framework of the discrete version in time of the path integral. In the framework of our approach, we obtained the response function for the spin fluctuations for the whole region of the frequency ω and the wave vector k and calculated the free energy of the system.
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From Pis’ma v Zhurnal Éksperimental’no\(\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{l} \) i Teoretichesko\(\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{l} \) Fiziki, Vol. 72, No. 10, 2000, pp. 746–752.
Original English Text Copyright © 2000 by Belinicher, da Providencia.
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Belinicher, V.I., da Providencia, J. Invariant spin coherent states and the theory of the quantum antiferromagnet in a paramagnetic phase. Jetp Lett. 72, 521–526 (2000). https://doi.org/10.1134/1.1343156
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DOI: https://doi.org/10.1134/1.1343156