H is the Hamiltonian. Here we set µ=0. For grand-canonical calculations add -6µ to the main diagonal.

-2*h + U	0	(-I)*Sqrt[3]*t
0	-2*h + U	((-3 - I*Sqrt[3])*t)/Sqrt[2]
I*Sqrt[3]*t	(I*(3*I + Sqrt[3])*t)/Sqrt[2]	-2*h + U