Thermodynamics of the Spin Luttinger-Liquid in a Model Ladder Material
  The phase diagram in temperature and magnetic field of the metal-organic, two-leg, spin-ladder compound (C5H12N)2CuBr4 is studied by measurements of the specific heat and the magnetocaloric effect. We demonstrate the presence of an extended spin Luttinger-liquid phase between two field-induced quantum critical points and over a broad range of temperature. Based on an ideal spin-ladder Hamiltonian, comprehensive numerical modelling of the ladder specific heat yields excellent quantitative agreement with the experimental data across the complete phase diagram. 
Ch. R\"uegg, K. Kiefer, B. Thielemann, D. F. McMorrow, V. Zapf, B.   Normand, M. B. Zvonarev, P. Bouillot, C. Kollath, T. Gi...