Superfluid-Insulator Transition and Fermion Pairing in Bose-Fermi Mixtures

TL;DR

This paper investigates how the presence of fermions affects the superfluid-insulator transition in Bose-Fermi mixtures, revealing modifications in critical behavior and discussing fermion pairing mediated by quantum critical fluctuations.

Contribution

It demonstrates that fermions can alter the nature of the superfluid-insulator transition, making it either first order or a different second order, and explores fermion pairing mechanisms.

Findings

Fermions modify the critical properties of SIT with z=1, potentially inducing a first order transition.

The particle-hole asymmetric SIT with z=2 remains stable against fermion coupling.

Quantum critical fluctuations near SIT mediate pairing interactions between fermions.

Abstract

It is well known that bosons on an optical lattice undergo a second-order superfluid-insulator transition (SIT) when the lattice potential increases. In this paper we study SIT when fermions coexist with the bosons. We find that the critical properties of particle-hole symmetric SIT with dynamical exponent z=1 is modified when fermions are present; it either becomes a fluctuation-driven first order transition or a different second-order transition. On the other hand the more generic particle-hole asymmetric (with z=2) SIT is stable against coupling with fermions. We also discuss pairing interaction between fermions mediated by quantum critical fluctuations near SIT.