Frustration and time reversal symmetry breaking for Fermi and Bose-Fermi systems

TL;DR

This paper explores how breaking time-reversal symmetry in optical lattices induces complex tunneling, leading to novel superfluid phases and frustrated magnetism in Fermi and Bose-Fermi systems.

Contribution

It demonstrates the realization of complex tunneling amplitudes in optical lattices and their effects on superfluid pairing and magnetism in Fermi and Bose-Fermi mixtures.

Findings

Complex tunneling induces complex pairing functions.

Boson-fermion coupling influences fermionic superfluid phases.

Fermi systems can exhibit both gapped and gapless superfluidity.

Abstract

The modulation of an optical lattice potential that breaks time-reversal symmetry enables the realization of complex tunneling amplitudes in the corresponding tight-binding model. For a superfluid Fermi gas in a triangular lattice potential with complex tunnelings the pairing function acquires a complex phase, so the frustrated magnetism of fermions can be realized.Bose-Fermi mixture of bosonic molecules and unbound fermions in the lattice shows also an interesting behavior. Due to boson-fermion coupling, the fermions become slaved by the bosons and the corresponding pairing function takes the complex phase determined by bosons. In the presence of bosons the Fermi system can reveal both gap and gapless superfluidity.