Spin Gap of S=1/2 Heisenberg Ladder: Field Theoretical Study of Magnetic Susceptibility and NMR Relaxation Rate

抄録

The temperature dependence of the static spin susceptibility, χ, and NMR relaxation rate, T₁^-1, of S=1/2 Heisenberg two-leg ladder systems have been studied based on the Majorana fermion representation of the S=1/2 Heisenberg spin Hamiltonian introduced by Shelton, Nersesyan and Tsvelik (Phys. Rev. B 53 (1996) 8521). It is shown that in the case of SrCu₂O₃, we can fit the experimental data of χ and T₁^-1in terms of themassive Majorana fermion excitation withmass m=440 K to resolve the apparent discrepancy of the spin gap activation energies between χ and T₁^-1.