Al. Chernyshev et al., Long-range order and low-energy spectrum of diluted 2D quantum antiferromagnet - art. no. 067209, PHYS REV L, 8706(6), 2001, pp. 7209
The problem of a diluted two-dimensional quantum antiferromagnet on a squar
e lattice is studied using spin-wave theory. The influence of impurities on
static and dynamic properties is investigated and a good agreement with ex
periments and Monte Carlo data is found. The hydrodynamic description of sp
in waves breaks down at characteristic wavelengths Lambda greater than or s
imilar to exp(const/x), x being an impurity concentration, while the order
parameter is free from anomalies. We argue that this dichotomy originates f
rom strong scattering of the low-energy excitations in two dimensions.