Quantum-critical spin dynamics in a Tomonaga-Luttinger liquid studied   with muon-spin relaxation
  We demonstrate that quantum-critical spin dynamics can be probed in high magnetic fields using muon-spin relaxation ($\mu^{+}$SR). Our model system is the strong-leg spin ladder bis(2,3-dimethylpyridinium) tetrabromocuprate (DIMPY). In the gapless Tomonaga-Luttinger liquid phase we observe finite-temperature scaling of the $\mu^{+}$SR $1/T_1$ relaxation rate which allows us to determine the Luttinger parameter $K$. We discuss the benefits and limitations of local probes compared with inelastic neutron scattering. 
J. S. M\"oller, T. Lancaster, S. J. Blundell, F. L. Pratt, P. J.   Baker, F. Xiao, R. C. Williams, W. Hayes, M. M. Turnbull,...
cond-mat.str-el