Dynamical lattice instability versus spin liquid state in a frustrated   spin chain system
  The low-dimensional s=1/2 compound (NO)[Cu(NO3)3] has recently been suggested to follow the Nersesyan-Tsvelik model of coupled spin chains. Such a system shows unbound spinon excitations and a resonating valence bond ground state due spin frustration. Our Raman scattering study demonstrates phonon anomalies as well as the suppression of a broad magnetic scattering continuum for temperatures below a characteristic temperature, T<T*=100K. We interpret these effects as evidence for a dynamical interplay of spin and lattice degrees of freedom that might lead to a further transition into a dimerized or structurally distorted phase at lower temperatures. 
V. Gnezdilov, P. Lemmens, Yu. G. Pashkevich, D. Wulferding, I.V.   Morozov, O.S. Volkova, A. Vasiliev
cond-mat.str-el cond-mat.mtrl-sci