Motivated by work on the bulk topological proximity effect and the topological bootstrap, we consider two coupled layers of quantum anomalous Hall (QAH) insulators with opposite signs of time-reversal breaking, which leads to a trivial band insulator at half-filling. We study the impact of interactions in this model within slave rotor theory, which leads to a layer-selective Mott transition, resulting in a fractionalized quantum anomalous Hall insulator ${\mathrm{QAH}}^{*}$ where a Chern band insulator coexists with a chiral spin liquid. We also compute the edge electron spectral function in the vicinity of the ${\mathrm{QAH}}^{*}$ phase.

• Received 18 April 2018
• Revised 27 August 2018

DOI:https://doi.org/10.1103/PhysRevB.98.125145