Pairing of a few Fermi atoms in one dimension

We study a few Fermi atoms interacting through attractive contact forces in a one-dimensional trap by means of numerical exact diagonalization. From the combined analysis of energies and wave functions of correlated ground and excited states we find evidence of BCS-like pairing even for very few atoms. For moderate interaction strength, we reproduce the even-odd oscillation of the separation energy observed in Zürn, Wenz, Murmann, Bergschneider, Lompe, and Jochim, Phys. Rev. Lett. 111, 175302 (2013)PRLTAO0031-900710.1103/PhysRevLett.111.175302. For strong interatomic attraction the arrangement of dimers in the trap differs from the homogeneous case as a consequence of Pauli blockade in real space.