Thank you very much for your reply!
When you say 'capturing the correct energetics,' do you mean ensuring the proper singlet-triplet splitting (where the singlet is lower in energy)?
I'm reading "Lecture Notes on Electron Correlation and Magnetism" by P. Fazekas, and I came across a question regarding the form of the Heisenberg term in the t-J model.
In Chapter 5.1.4, the t-J model is written where there is an additional density-density term in the exchange interaction...
Hello, thank you all for the replies. I found the source of my error. I have wrongly defined the K point.
It should be:
# high symmetry points
Gamma = np.array([0, 0])
K = 2*np.pi*np.array([1/3, 1/np.sqrt(3)])
M = 2*np.pi*np.array([0, 1/(np.sqrt(3))])
with this convention we get the correct...
We need to define a high symmetry point path in the Brillouin zone, we can choose: Gamma-K-M-Gamma
My attempt:
import numpy as np
import matplotlib.pyplot as plt
# lattice vectors
a1 = np.array([1, 0])
a2 = np.array([-1/2, np.sqrt(3)/2])
a3 = -(a1 + a2)
a = [a1,a2,a3]
#high symmetry points...
To compute the Fourier transform of the ##t-V## model for the case where ##t = 0##, we start by expressing the Hamiltonian in momentum space. Given that the hopping term ##t## vanishes, we only need to consider the potential term:
$$\hat{H} = V \sum_{\langle i, j \rangle} \hat{n}_i \hat{n}_j$$...