We study the magnetic-field-induced quantum phase transition from a gapped quantum phase that has no magnetic long-range order into a gapless phase in the spin-1/2 ladder compound bis(2,3-dimethylpyridinium) tetrabromocuprate (DIMPY). At temperatures below about 1a K, the specific heat in the gapless phase attains an asymptotic linear temperature dependence, characteristic of a Tomonaga-Luttinger liquid. Inelastic neutron scattering and the specific heat measurements in both phases are in good agreement with theoretical calculations, demonstrating that DIMPY is the first model material for an S=1/2 two-leg spin ladder in the strong-leg regime. © 2010 The American Physical Society.
Keyword: Tetrabromocuprate,Specific heat,Theoretical calculations,Specific heat measurement,Ladders,Ladder compounds,Thermal variables measurement,Phase transitions,Quantum phase,Tomonaga Luttinger liquid,Calorimetry,Long range orders,Linear temperature dependence,Model materials,S=1/2 two-leg spin ladder,Liquids,Quantum phase transitions