Evidence for a Strong Topological Insulator Phase in $\mathrm{ZrTe_5}$
  The complex electronic properties of $\mathrm{ZrTe_5}$ have recently stimulated in-depth investigations that assigned this material to either a topological insulator or a 3D Dirac semimetal phase. Here we report a comprehensive experimental and theoretical study of both electronic and structural properties of $\mathrm{ZrTe_5}$, revealing that the bulk material is a strong topological insulator (STI). By means of angle-resolved photoelectron spectroscopy, we identify at the top of the valence band both a surface and a bulk state. The dispersion of these bands is well captured by ab initio calculations for the STI case, for the specific interlayer distance measured in our x-ray diffraction study. Furthermore, these findings are supported by scanning tunneling spectroscopy revealing the metallic character of the sample surface, thus confirming the strong topological nature of $\mathrm{ZrTe_5}$. 
G. Manzoni, L. Gragnaniello, G. Aut\`es, T. Kuhn, A. Sterzi, F.   Cilento, M. Zacchigna, V. Enenkel, I. Vobornik, L. Barba, ...
cond-mat.mtrl-sci