 
Summary: VOLUME 81, NUMBER 4 P H Y S I C A L R E V I E W L E T T E R S 27 JULY 1998
Square Patterns in RayleighBénard Convection with Rotation about a Vertical Axis
Kapil M. S. Bajaj, Jun Liu, Brian Naberhuis, and Guenter Ahlers
Department of Physics and Center for Nonlinear Science, University of California, Santa Barbara, California 93106
(Received 26 January 1998)
We present experimental results for RayleighBénard convection with rotation about a vertical axis at
dimensionless rotation rates 0 # V # 250 and e DT DTc 2 1 & 0.2. Critical Rayleigh numbers
and wave numbers agree with predictions of linearstability analysis. For V * 70 and small e the
patterns are cellular with local fourfold coordination and differ from the theoretically expected Küppers
Lortz unstable state. Stable as well as intermittent defectfree square lattices exist over certain parameter
ranges. Over other ranges defects dynamically disrupt the lattice but cellular flow and local fourfold
coordination is maintained. [S00319007(98)066964]
PACS numbers: 47.54.+r, 47.20.Lz, 47.27.Te
The elucidation of spatiotemporal chaos (STC) remains
one of the major tasks in the study of pattern formation in
nonlinear dissipative systems [1]. The best opportunities
for theoretical understanding of experimental observations
of a chaotic state exist when the meansquare amplitude
of STC evolves continuously (i.e., via a supercritical bi
furcation) from a spatially uniform ground state; for in
