Hi
I'm trying to get the gap (between the Sz=0 sector and the Sz=1/2 i.e. spinon) for a spin-1/2 anti-ferromagnetic Hiesenberg chain for a finite system L=4. No eigenvalues are calculated in the output file when I perform sparse diagonalization on the below parameter file for getting the spinon eigenvalue:
MODEL="spin"; LATTICE="chain lattice"; LATTICE_LIBRARY="../lattices.xml" MODEL_LIBRARY="../models.xml" CONSERVED_QUANTUMNUMBERS="Sz"; local_S=1/2; J=1; {L=4; Sz_total=1/2;}
It seems only the sectors with Sz= {-1,0,+1} can be input to the Lanczos algorithm. Can somebody tell me what I am missing?
Thanks, Vipin