  A novel class of non-local interactions between bosons is found to favor a
crystalline Bose-Einstein condensation ground state. By using both low energy
effective field theory and variational wavefunction method, we compare this
state not only with the homogeneous superfluid, as has been done previously,
but also with the normal (non-superfluid) crystalline phase and obtain the
phase diagram. The key characters are: the interaction potential displays a
negative minimum at finite momentum which determines the wavevector of this
supersolid phase; and the wavelength corresponding to the momentum minimum
needs to be greater than the mean inter-boson distance.
