Wilson ratio of a Tomonaga-Luttinger liquid in a spin-1/2 Heisenberg   ladder
  Using micromechanical force magnetometry, we have measured the magnetization of the strong-leg spin-1/2 ladder compound (C$_7$H$_{10}$N)$_2$CuBr$_2$ at temperatures down to 45 mK. Low-temperature magnetic susceptibility as a function of field exhibits a maximum near the critical field H_c at which the magnon gap vanishes, as expected for a gapped one-dimensional antiferromagnet. Above H_c a clear minimum appears in the magnetization as a function of temperature as predicted by theory. In this field region, the susceptibility in conjunction with our specific heat data yields the Wilson ratio R_W. The result supports the relation R_W=4K, where K is the Tomonaga-Luttinger-liquid parameter. 
K. Ninios, Tao Hong, T. Manabe, C. Hotta, S. N. Herringer, M. M.   Turnbull, C. P. Landee, Y. Takano, H. B. Chan
cond-mat.str-el