Topological charge pumping in a Fermi gas with Hubbard interactions

We consider charge pumping in one-dimensional interacting systems of spinful fermions, where each species is described by a (possibly shifted) Rice-Mele model.The ionic Hubbard model [1-3] is visited twice during a pump cycle. It hosts three phases: The Mott-Insulating (MI) phase is separated from the band-insulating (BI) phase via a spontaneously dimerized (SDI) phase. A dimerized hopping connects the BI and MI phases without closing the charge gap. We show via the many-body polarization and time-dependent calculations of the integrated current that a closed loop around one charge critical point of the ionic Hubbard model leads to the pumping of a single unit of charge per pump cycle in the adiabatic limit, as opposed to two charges for a usual Rice-Mele pump. Pumping through the SDI phase does not change the quantization of pumped charge, contrary to what was recently reported in [4].

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[2] Torio et al., Phys. Rev. B 73, 115109 (2006).

[3] Manmana et al., Phys. Rev. B 70, 155115 (2004).

[4] Nakagawa et al., Phys. Rev. B 98, 115147 (2018).