  We propose a novel formulation of the Interacting Boson Model (IBM) for
rotational nuclei with axially-symmetric strong deformation. The intrinsic
structure represented by the potential energy surface (PES) of a given
multi-nucleon system has a certain similarity to that of the corresponding
multi-boson system. Based on this feature, one can derive an appropriate boson
Hamiltonian as already reported. This prescription, however, has a major
difficulty in rotational spectra of strongly deformed nuclei: the bosonic
moment of inertia is significantly smaller than the corresponding nucleonic
one. We present that this difficulty originates in the difference between the
rotational response of a nucleon system and that of the corresponding boson
system, and could arise even if the PESs of the two systems were identical. We
further suggest that the problem can be cured by implementing $\hat{L} \cdot
\hat{L}$ term into the IBM Hamiltonian, with coupling constant derived from the
cranking approach of Skyrme mean-field models. The validity of the method is
confirmed for rare-earth and actinoid nuclei, as their experimental rotational
yrast bands are reproduced nicely.
