Composite Fermions and their Pair States in a Strongly-Coupled Fermi Liquid

TL;DR

This paper investigates the formation of composite fermions and bosons in strongly-coupled Fermi liquids within optical lattices, revealing new pair states, mass dressing effects, and a quantum critical point associated with Bose-Einstein condensation.

Contribution

It introduces a strong-coupling theoretical framework for fermions in optical lattices, uncovering novel composite fermions and bosons, and analyzes their condensation behavior and quantum criticality.

Findings

Discovery of massive composite fermions coupled to bosons in high dimensions

Identification of a critical temperature for BEC of composite bosons

Prediction of a quantum critical point related to condensate formation

Abstract

Our goal is to understand the phenomena arising in optical lattice fermions at low temperature in an external magnetic field. Varying the field, the attraction between any two fermions can be made arbitrarily strong, where composite bosons form via so-called Feshbach resonances. By setting up strong-coupling equations for fermions, we find that in spatial dimension $d>2$ they couple to bosons which dress up fermions and lead to new massive composite fermions. At low enough temperature, we obtain the critical temperature at which composite bosons undergo the Bose-Einstein condensate (BEC), leading to BEC-dressing massive fermions. These form tightly bound pair states which are new bosonic quasi-particles producing a BEC-type condensate. A quantum critical point is found and the formation of condensates of complex quasi-particles is speculated over.