Hi ITensor team,

Thanks for your wonderful software ! I want to calculate Haldane string operator correlation function, so I want to define string operator, for example <\prod*{n<I}exp(I\pi S*{n}^{z})S^{z}_{I}>.if I have string operator, then I can calculate correlation function as spin correlation function. But I don't know how to exponential operator Sz(maybe MPO). my naive partial code as follow:

auto phi1=expHermitian(sites.op("Sz",1),PI*Cplx_i);
auto phi2=expHermitian(sites.op("Sz",1),PI*Cplx_i);

for(int n = 2; n < N/4; ++n)

{

phi1 *=expHermitian(sites.op("Sz",n),PI*Cplx_i);

print(phi1);

}

auto Ss1 = phi1*sites.op("Sz",N/4);

for(int n = 2; n < 3*N/4; ++n)
{
phi2 *=expHermitian(sites.op("Sz",n),PI*Cplx_i);

}

auto Ss2 = phi2*sites.op("Sz",3*N/4);

Ss1 and Ss2 is string operator at N/4 and 3*N/4. BUT this code does't work. Please help me to check. Thank you !