Matrix H in Subspace 141 with Dimension 3

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