We study three-body recombination in two dimensions for systems interacting via short-range two-body interactions in the regime of large scattering lengths. Using the adiabatic hyperspherical representation, we derive semianalytical formulas for three-body recombination in both weakly and deeply bound diatom states. Our results demonstrate the importance of long-range corrections to the three-body potentials by showing how they alter the low-energy and scattering-length dependence of the recombination rate for both bosonic and fermionic systems, which exhibit suppressed recombination if compared to the three-dimensional case. We verify these results through numerical calculations of recombination for systems with finite-range interactions and supporting a few two-body bound states. We also study finite-range effects for the energies of the universal three-identical-bosons states and find a slow approach to universal predictions as a function of the scattering length.
On the three-body kinematics, we investigate the threshold behavior which appears not only at the three-body break-up threshold (3BT), but also at the quasi two-body threshold (Q2T) for the reactions:
A+(BC)→A+B+C , and
(ABC)→A+(BC) , respectively. Recently, the author proposed a general particle
transfer (GPT) potential which appears, not only at the 3BT, but also at the Q2T between A and (BC). The new potential indicates a Yukawa-type potential for short range, but a
1/rn -type potential for long range. The long range part of the GPT potential for
n=1 indicates an attractive Coulomb-like or a gravitation-like potential. While,
n=2 indicates the Efimov-like potential between A and (BC). The three-body binding energy:
En=ϵ+ζn with the two-body binding energy
ϵ , and the separation energy
ζn for
(ABC)→A+(BC) satisfies
En/En+1=ζn/ζn+1 =const for
ϵ=0 or the two-body scattering length:
a→∞ (i.e. the two-body unitary limit). At the Q2T, the condensation of the three-body binding energy is given by the GPT-potential in the form of
En/En+1=(ζn+ϵ)/(ζn+1+ϵ)→1 (const) for
n→∞ (with
ζn→0 ) which implies the existence of Efimov-like states at the Q2T in the hadron systems, thereby the possibility of “ultra low energy nuclear transformation”, where the three-body binding energies degenerate at zero energy. Finally, the origin of such a long range potential will be clarified.