Experimental evidence of large-gap two-dimensional topological insulator   on the surface of ZrTe5
  Two-dimensional (2D) topological insulators (TIs) with a large bulk band-gap are promising for experimental studies of the quantum spin Hall effect and for spintronic device applications. Despite considerable theoretical efforts in predicting large-gap 2D TI candidates, only few of them have been experimentally verified. Here, by combining scanning tunneling microscopy/spectroscopy and angle-resolved photoemission spectroscopy, we reveal that the top monolayer of ZrTe5 crystals hosts a large band gap of ~100 meV on the surface and a finite constant density-of-states within the gap at the step edge. Our first-principles calculations confirm the topologically nontrivial nature of the edge states. These results demonstrate that the top monolayer of ZrTe5 crystals is a large-gap 2D TI suitable for topotronic applications at high temperature. 
R. Wu, J.-Z. Ma, L.-X. Zhao, S.-M. Nie, X. Huang, J.-X. Yin, B.-B. Fu,   P. Richard, G.-F. Chen, Z. Fang, X. Dai, H.-M. Weng...
cond-mat.mtrl-sci cond-mat.mes-hall