The ground-state properties and the soft dipole mode of the He-6 nucle
us are investigated by the coupled-rearrangement-channel variational m
ethod based on an alpha + n + n cluster model, where the effect of the
Pauli principle between the alpha core and valence neutrons is taken
into account. A reasonable binding energy is obtained for the ground s
tate with the use of realistic nn and nalpha interactions. The resulti
ng ground-state wave function has a long-range tail in the neutron dis
tribution, clearly indicating the neutron halo structure in the He-6 n
ucleus. The calculated distribution of the electric-dipole transition
to the 1- excited states shows a localization of the strength to a rat
her broad peak around E(x) congruent-to 2.5 MeV with a width of about
4 MeV.