摘要
Generally,the topological corner state in two-dimensional(2D)second-order topological insulator(SOTI)is equivalent to the well-known domain wall state,which is originated from the mass-inversion between two adjacent edges with phase shift ofπ.In this work,go beyond this conventional physical picture,we report a fractional mass-kink induced 2D SOTI in monolayer FeSe with canted checkerboard antiferromagnetic(AFM)order by analytic model and first-principles calculations.The canted spin associated in-plane Zeeman field can gap out the quantum spin Hall edge state of FeSe,forming a fractional mass-kink with phase shift ofπ/2 at the rectangular corner,and generating an in-gap topological corner state with fractional charge of e/4.Moreover,the topological corner state is robust to a finite perturbation,existing in both naturally and non-naturally cleaved corners,regardless of the edge orientation.Our results not only demonstrate a material system to realize the unique 2D AFM SOTI,but also pave a way to design the higher-order topological states from fractional mass-kink with arbitrary phase shift.
基金
This work was supported by NSFC(Grant No.12174369,11774325,and 21603210)
National Key Research and Development Program of China(Grant No.2017YFA0204904)
Fundamental Research Funds for the Central Universities.
