https://doi.org/10.1007/s100510050434
Flow equations and extended Bogoliubov transformation for the Heisenberg antiferromagnet near the classical limit
Institut für Theoretische Physik,
Ruprecht-Karls-Universität Heidelberg,
Philosophenweg 19, 69120 Heidelberg, Germany
Corresponding author: a stein@tphys.uni-heidelberg.de
Received:
19
March
1998
Revised:
2
June
1998
Accepted:
8
June
1998
Published online: 15 September 1998
The Heisenberg spin-S quantum antiferromagnet is studied near
the large-spin
limit, applying a new continuous unitary transformation which extends
the usual Bogoliubov transformation to higher order in the 1/S-expansion
of the Hamiltonian. This allows to
diagonalize the bosonic Hamiltonian resulting from the Holstein-Primakoff
representation beyond the conventional spin-wave approximation.
The zero-temperature flow equations derived from the extension of the
Bogoliubov transformation to order 
for the ground-state energy, the spin-wave velocity, and
the staggered magnetization are solved exactly and yield results
which are in agreement with those obtained by
a perturbative treatment of the magnon interactions.
PACS: 75.10.Jm – Quantized spin models / 71.27.+a – Strongly correlated electron systems; heavy fermions
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 1998
