  Correlations between low-lying electric dipole (E1) strength and neutron skin
thickness are systematically investigated with the fully self-consistent
random-phase approximation using the Skyrme energy functionals. The presence of
strong correlation among these quantities is currently under dispute. We find
that the strong correlation is present in properly selected nuclei, namely in
spherical neutron-rich nuclei in the region where the neutron Fermi levels are
located at orbits with low orbital angular momenta. The significant correlation
between the fraction of the energy-weighted sum value and the slope of the
symmetry energy is also observed. The deformation in the ground state seems to
weaken the correlation.
