Matrix H in Subspace 15 with Dimension 4

H is the Hamiltonian. Here we set µ=0. For grand-canonical calculations add -6µ to the main diagonal.
-4*h + U ((-1 - I*Sqrt[3])*t)/Sqrt[2] 0 0
(I*(I + Sqrt[3])*t)/Sqrt[2] -4*h + U (-I/2)*(-I + Sqrt[3])*t 0
0 (I/2)*(I + Sqrt[3])*t -4*h + U ((-1 - I*Sqrt[3])*t)/Sqrt[2]
0 0 (I*(I + Sqrt[3])*t)/Sqrt[2] -4*h