  We calculated, using seven realistic 4He-4He potentials in the literature,
the Efimov spectra of the 4He trimer and tetramer and analyzed the universality
of the systems. The three-(four-)body Schroedinger equations were solved fully
nonadiabatically with the high-precision calculation method employed in our
previous work on the 4He trimer and tetramer [Phys. Rev. A 85, 022502 (2012);
85, 062505 (2012)]. We found the following universality in the four-boson
system: i) The critical scattering lengths at which the tetramer ground and
excited states couple to the four-body threshold are independent of the choice
of the two-body realistic potentials in spite of the difference in the
short-range details and do not contradict the corresponding values observed in
the experiments in ultracold alkali atoms when scaled with the van der Waals
length r_vdW, and ii) the four-body hyperradial potential has a repulsive
barrier at the four-body hyperradius R_4 \approx 3 r_vdW, which prevents the
four particles from getting close together to explore nonuniversal features of
the interactions at short distances. This result is an extension of the
universality in Efimov trimers that the appearance of the repulsive barrier at
the three-body hyperradius R_3 \approx 2 r_vdW makes the critical scattering
lengths independent of the short-range details of the interactions as reported
in the literature and also in the present work for the 4He trimer with the
realistic potentials.
