You can tell ALPS to measure the magnetization as expectation value of Sz. Which code did you plan on using? Are you in Santa Barbara this week? If so, we can meet and I can help you directly since I'm in SB until August 2.

Matthias

On Jul 12, 2008, at 1:39 AM, Gang Chen wrote:

Hi All,

Sorry to bother, I have a question about spin susceptibility. In my problem, the total spin is not a good quantum number. If I apply exact diagonalization code, how do I obtain spin susceptibility? One thing you might suggest is to measure total spin Sz (say the applied magnetic field is along z direction), and calculate \chi approximated as (<S_z>_h - <S_z>_{h=0}) /h. Then how to ask ALPS to measure <S_z>? Same question for quantum monte carlo.

Could anyone be kind to offer a help?

Thanks,

GANG CHEN Department of Physics U.C. Santa Barbara