Two-flavour mixture of a few fermions of different mass in a one-dimensional harmonic trap

A system of two species of fermions of different mass confined in a one-dimensional harmonic trap is studied with an exact diagonalization approach. It is shown that a mass difference between fermionic species induces a separation in the density of the lighter flavour independently of the number of particles. The mechanism behind the emergent separation is explained phenomenologically and confirmed by direct studies of the ground state of the system. Finally, it is shown that the separation driven by a mass difference, in contrast to the separation induced by a difference of populations, is robust to the interactions with a thermal environment.