Phases and collective modes of a hardcore Bose-Fermi mixture in an optical lattice

2008/11/30 by S. Sinha, Subhasis Sinha, K. Sengupta
Physics and Astronomy · #Boson #Cold Atom Physics and Bose-Einstein Condensates #Condensed matter physics #Fermion #Hubbard model #Mott insulator #Mott transition #Optical lattice #Phase (matter) #Phase diagram #Phase transition #Physics #Physics of Superconductivity and Magnetism #Quantum mechanics #Quantum phase transition #Quantum, superfluid, helium dynamics #Superconductivity #Superfluidity #Supersolid #cond-mat.str-el

paper · pdf · doi:10.1103/physrevb.79.115124

10 pages 6 Figs v2: Updated version with more refs and additional discussions

arxiv created 2008/12/08 · openalex publication_date 2009/03/24 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

We obtain the phase diagram of a Bose-Fermi mixture of hardcore spinless bosons and spin-polarized fermions with nearest-neighbor intraspecies interaction and on-site interspecies repulsion in an optical lattice at half filling using a slave-boson mean-field theory. We show that such a system can have four possible phases which are (a) supersolid bosons coexisting with fermions in the Mott state, (b) Mott state of bosons coexisting with fermions in a metallic or charge-density wave state, (c) a metallic fermionic state coexisting with superfluid phase of bosons, and (d) Mott insulating state of fermions and bosons. We chart out the phase diagram of the system and provide analytical expressions for the phase boundaries within mean-field theory. We demonstrate that the transitions between these phases are generically first order with the exception of that between the supersolid and the Mott states which, within mean-field theory, is a continuous quantum phase transition. We also obtain the low-energy collective excitations of the system in these phases. Finally, we study the particle-hole excitations in the Mott insulating phase and use it to determine the dynamical critical exponent z for the supersolid-Mott insulator transition. We discuss experiments which can test our theory.

Citations

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