Interaction-Split Edge Spectral Flow in an Integer Hubbard Thouless Pump

Abstract

We show that local Hubbard correlations can split the open-boundary spectral flow of an otherwise integer Thouless pump. Using density-matrix renormalization group calculations for a period-three Hubbard chain with a sliding onsite-repulsion modulation, we identify at filling $\ddot{I}=2/3$ a correlated insulating pump with many-body Chern number $C=+2$, corresponding to two units of charge transported per cycle. A spin-degenerate Hartree/Aubry--André--Harper reference model realizes the same integer response through simultaneous edge spectral flow in two independent spin channels. In the full Hubbard model, however, this integer bulk pump is implemented differently at an open boundary: the edge flow separates into two boundary events, and the intervening low-energy state is a nearly charge-neutral triplet edge excitation. Thus the quantized bulk charge transport remains integer, but local correlations reorganize its boundary realization into separated charged and neutral spinful sectors.

6 pages, 4 figures, plus Supplemental Material (7 pages, 10 figures)