  CsCuCl3 is a quantum triangular antiferromagnet, ferromagnetically stacked,
with an incommensurate (IC) structure due to a Dzyaloshinskii-Moriya
interaction. Because of the classical degeneracy caused by the frustration,
fluctuations in CsCuCl3 have extraordinarily large effects, such as the phase
transition in longitudinal magnetic field (normal to 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 T. Werner et
al. [Solid State Commun. 102, p.609 (1997)]. We develop and analyse the
corresponding minimal Landau theory; the effects of fluctuations on the
frustration are included phenomenologically, by means of a biquadratic term.
The Landau theory gives two IC phases, one familiar from previous studies;
properties of the new IC phase, which occupies a pocket of the
temperature-field phase diagram near T_N, agree qualitatively with those of the
new phase found experimentally.
