Finite size study of the spin-1/2 dimerised Heisenberg chain

The authors present the results of a finite size analysis of the one-dimensional spin-1/2 dimerised Heisenberg chain. The value of the gap exponent, nu , is obtained using two extrapolation procedures. When logarithmic corrections are taken into account, they obtain the values nu =0.668+or-0.001 and nu =0.667+or-0.002, in good agreement with the conjectured value nu =2/3. They compare these results with those obtained assuming a pure power-law behaviour.