Generates the plot on the convergenge of the mean field in single
       site spin hamiltonian under with N degenerate half-filled orbitals

def plot_mean_field_conv(N=1, n=0.5, Uspan=np.arange(0, 3.6, 0.5)):
    """Generates the plot on the convergenge of the mean field in single
       site spin hamiltonian under with N degenerate half-filled orbitals """

    sl = Spinon(slaves=2*N, orbitals=N, avg_particles=2*n,
                       hopping=[0.5]*2*N, orbital_e=[0]*2*N)
    hlog = solve_loop(sl, Uspan, [0.])[1]

    f, (ax1, ax2) = plt.subplots(2, sharex=True)
    for field in hlog:
        field = np.asarray(field)
        ax1.semilogy(abs(field[1:]-field[:-1]))
        ax2.plot(field)#, label = 'h, U = {}'.format(Uint))

    plt.title('Convergence of selfconsintent mean field')
    ax1.set_ylabel('$\\Delta h$')
    ax2.set_ylabel('mean field $h$')
    plt.xlabel('iterations')

    return hlog