Abstract
ABSTRACT
The functional quantum spin Hall insulators (QSHI), protected by time‐reversal symmetry against single‐particle backscattering, hold great promise for dissipationless quantum electronics. Realization of QSHI with gapped helical edge states, which would enable deterministic on/off switching of the edge‐channel conductance is a key requirement for programmable topological circuits. Here, we report realization of superlattice‐modulated QSHI HfTe
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hosting emergent multigap‐like helical edge states. Using scanning tunneling microscopy and spectroscopy, we identify a reconstruction‐induced periodic superlattice modulation in epitaxial monolayer HfTe
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and directly observe multiple gap‐like features in the edge channel, accompanied by a series of sharp peaks in the density of states. Combined with theoretical modelling, we attribute the observed edge gap to the finite‐width coupling between the two edges significantly enhanced by the superlattice modulation, whereas the sharp peaks are the manifestations of mini‐gaps opening at the reduced Brillouin zone boundaries by the periodic modulation of spin‐orbit coupling. Notably, these sharp peaks exhibit clear Zeeman splitting under magnetic fields, consistent with the helical nature of the topological edge states. Our results establish a viable route to engineering gapped helical edge states in QSHI and provide a promising platform for topological devices with desired on/off switchability.