Charge and spin gaps in the ionic Hubbard model with density-dependent hopping

Abstract

We calculate the charge gap ΔEC and the spin gap ΔES of the ionic Hubbard chain including electron-hole symmetric density-dependent hopping. The vanishing of ΔEC (ΔES) signals a quantum critical point in the charge (spin) sector. Between both critical points, the system is a fully gapped spontaneously dimerized insulator. We focus our study in this region. Including alternation in the hopping, it is possible to perform an adiabatic Thouless pump of one charge per cycle, but with a velocity limited by the size of the gaps.