Crystalline phase of strongly interacting Fermi mixtures

TL;DR

This paper predicts a quantum phase transition to a crystalline state in a mixture of heavy and light fermionic atoms, driven by long-range repulsion and a critical mass ratio, with potential experimental observation in optical lattices.

Contribution

It introduces the concept of a gas-crystal quantum transition in fermionic mixtures based on mass ratio and long-range interactions, supported by calculations.

Findings

Critical mass ratio for crystallization exceeds 100.

Crystalline order can be observed as a superlattice in optical lattices.

System remains stable against molecular relaxation and trimer formation.

Abstract

We show that the system of weakly bound molecules of heavy and light fermionic atoms is characterized by a long-range intermolecular repulsion and can undergo a gas-crystal quantum transition if the mass ratio exceeds a critical value. For the critical mass ratio above 100 obtained in our calculations, this crystalline order can be observed as a superlattice in an optical lattice for heavy atoms with a small filling factor. We also find that this novel system is sufficiently stable with respect to molecular relaxation into deep bound states and to the process of trimer formation.