Among the numerous topological insulating materials predicted, ideal topological materials with well separated Dirac crossings located near EF only take a limited fraction and are advantageous for spintronic applications. Bismuth halide system is such an ideal candidate as a weak topological insulator (WTI). In our work recently published in Physical Review B, “Ideal weak topological insulator and protected helical saddle points“, we have designed the ideal WTI Bi4I1.2Br2.8 and observed the surface Dirac and helical saddle points both inside the bulk band gap of 195 meV. This indicates the realization of an ideal WTI and a fertile ground for topological many-body physics.
Our work on the design and observation of an ideal weak topological insulator is published at PRB!