Superfluid-insulator transition and fermion pairing in Bose-Fermi mixtures
Kun Yang

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, and show that the fermion pairing/superfluid transition temperature peaks near SIT when a single species of fermion is present.

© 2008 The American Physical Society.