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Phys. Rev. B 78, 220504(R) (2008) [4 pages]

Boson Hubbard model with weakly coupled fermions

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Roman M. Lutchyn1,2, Sumanta Tewari1,3, and S. Das Sarma1
1Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
2Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
3Department of Physics and Astronomy, Clemson University, Clemson, South Carolina 29634, USA

Received 15 October 2008; published 8 December 2008

Using an imaginary-time path integral approach, we develop the perturbation theory suited to the boson Hubbard model and apply it to calculate the effects of a dilute gas of spin-polarized fermions weakly interacting with the bosons. The full theory captures both the static and the dynamic effects of the fermions on the generic superfluid-insulator phase diagram. We find that, in a homogenous system described by a single-band boson Hubbard Hamiltonian, the intrinsic perturbative effect of the fermions is to generically suppress the insulating lobes and to enhance the superfluid phase.

© 2008 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.78.220504
DOI:
10.1103/PhysRevB.78.220504
PACS:
64.70.Tg, 03.75.Lm, 03.75.Mn, 67.60.Fp
 
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