Ae. Jacobs et T. Nikuni, FLUCTUATION-INDUCED PHASE IN CSCUCL3 IN A TRANSVERSE MAGNETIC-FIELD -THEORY, Journal of physics. Condensed matter, 10(28), 1998, pp. 6405-6416
CsCuCl3 is a quantum triangular antiferromagnet. ferromagnetically sta
cked, with an incommensurate (IC) structure due to a Dzyaloshinskii-Mo
riya interaction. Because of the classical degeneracy caused by the fr
ustration, fluctuations in CsCuCl3 have extraordinarily large effects,
such as the phase transition in longitudinal magnetic field (normal t
o the planes, parallel to the IC wavenumber q) and the plateau in q in
transverse field (perpendicular to q). We argue that fluctuations are
responsible also for the new IC phase discovered in transverse field
near the Neel temperature T-N, by Werner et al (Werner T, Weber H B, W
osnitza J, Kelnberger A, Meschke M, Schotte U, Stusser N, Ding Y and W
inkelmann M 1997 Solid State Commun. 102 609). We develop and analyse
the corresponding minimal Landau theory; the ground-state reconstructi
on due to fluctuations is described phenomenologically, by means of a
biquadratic term. The Landau theory gives two IC phases, one familiar
from previous studies; the properties of the new IC phase, which occup
ies a pocket of the temperature-held phase diagram near T-N, agree qua
litatively with those of the new phase found experimentally.