Static and dynamic magnetic properties of coupled spin-1/2 antiferromagnetic chains

Calculations of the thermodynamic quantities, and the spectra of spinons, t riplet excitations, and two-particle spin-singlet (Delta S-z = 0, +/- 1) ex citations for a weakly coupled antiferromagnetic S = 1/2 spin chain are mad e using a mean-field approximation for the interchain couplings (J(2)) by t he quantum Monte Carlo method. The mass gaps in these excitation spectra ar e estimated as functions of the interchain coupling. The critical held H-c, and the temperatures at which the spinon and singlet gaps close (T-1 and T -2, respectively) are obtained. Some peculiarities of the staggered magneti zation, the specific heat, and the spin-spin correlation function are found at T-1 = 0.9J(2), T-2 = 1.5J(2), H-c = 3.8J(2), as determined by linear fu nction fitting for J(2)/J(1) < 0.15 The intrachain and interchain couplings , and the staggered magnetization for KCuF3, Sr2CuO3, and Ca2CuO3 are estim ated, and mass gaps are predicted to exist in the spectra of the spinons an d the singlet two-particle excitations.