Universal properties of the Four-Boson system in two dimensions

Artikel i vetenskaplig tidskrift, 2004

We consider the nonrelativistic four-boson system in two dimensions interacting via a short-range attractive potential. For a weakly attractive potential with one shallow two-body bound state with binding energy B-2, the binding energies B-N of shallow N-body bound states are universal and thus do not depend on the details of the interaction potential. We compute the four-body binding energies in an effective quantum mechanics approach. There are exactly two bound states: the ground state with B-4((0)) = 197.33(1)B-2 and one excited state with B-4((1)) = 25.5 (1)B-2. We compare our results to recent predictions for N-body bound states with large N much greater than 1.