Visualizing a Bosonic Symmetry Protected Topological Phase in an Interacting Fermion Model

摘要

Symmetry protected topological (SPT) phases in free fermion and interactingbosonic systems have been classified, but the physical phenomena of interactingfermionic SPT phases have not been fully explored. Here, employing large-scalequantum Monte Carlo simulation, we investigate the edge physics of a bilayerKane-Mele-Hubbard model with zigzag ribbon geometry. Our unbiased numericalresults show that the fermion edge modes are gapped out by interaction, whilethe bosonic edge modes remain gapless at the $(1+1)d$ boundary, before the bulkquantum phase transition to a topologically trivial phase. Therefore, finitefermion gaps both in the bulk and on the edge, together with the robust gaplessbosonic edge modes, prove that our system becomes an emergent bosonic SPT phaseat low energy, which is, for the first time, directly observed in aninteracting fermion lattice model.