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

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