Persistent currents, deformation and collectivity in the many-boson yrast problem on the circle

Properties of the yrast states of a system of $N$ bosons confined to a one-dimensional ring and interacting via contact forces is examined both variationally and by numerical diagonalizations. The latter allow for obtaining numerical correlated many-body wave functions explicitly. The study of correlation functions involving different yrast states indicates that a quantum phase transition previously detected in the properties of the ground state in the case of attractive two-body interactions is an yrast phenomenon involving the onset of deformation', in the sense given to this term by Bohr and Mottelson in connection with the description of nuclear spectra, including enhanced transition operators and emergence of a shared intrinsic correlation structure. In this case the moment of inertia of the deformed state is essentially the rigid moment of inertia, intrinsic’ states being essentially degenerate.