1.5. J1-J2 Heisenberg model¶
Here, we solve the
where
An input file (samples/tutorial_1.5/stan1.in
) for treating
model = "Spin"
method = "CG"
lattice = "square"
L = 4
W = 4
J = 1
J' = 1
2S = 1
2Sz = 0
exct = 4
Here, J (J’) represents
1.5.1. Calculations of spin structure factors for ground state¶
First, we calculate the spin structure factors, which are defined as
To calculate samples/tutorial_1.5/MakeGreen.py
),
you can generate greentwo.def for calculating samples/tutorial_1.5/input.txt
) is necessary,
whose form is given as follows
Lx 4
Ly 4
Lz 1
orb_num 1
Here, Lx (orb_num) represents the length of the x direction (number of orbitals).
By using a python script CalcSq.py (samples/tutorial_1.5/CalcSq.py
),
you can calculate
- Procedure for calculating and visualizing
is given as follows :: HPhi -sdry stan.in
python3 MakeGreen.py (input.txt is necessary)
HPhi -e namelist.def
python3 CalcSq.py (input.txt is necessary)
You can obtain Sq_eigen0.dat !!
splot “Sq_eigen0.dat” u 1:2:3 (using gnuplot)
Following the procedure, please see how

1.5.2. Calculations of spin structure factors for excited states¶
By changing exct in stan.in, you can obtain several excited states.
For those excited states, by changing max_num=1 in CalcSq.py as,
for example, max_num=4,
you can obtain
Please see how