The topological materials have attracted much attention for their unique electronic structure and peculiar physical properties. ZrTe₅ has host a long-standing puzzle on its anomalous transport properties manifested by its unusual resistivity peak and the reversal of the charge carrier type. It is also predicted that single-layer ZrTe₅ is a two-dimensional topological insulator and there is possibly a topological phase transition in bulk ZrTe₅. Here we report high-resolution laser-based angle-resolved photoemission measurements on the electronic structure and its detailed temperature evolution of ZrTe₅. Our results provide direct electronic evidence on the temperature-induced Lifshitz transition, which gives a natural understanding on underlying origin of the resistivity anomaly in ZrTe₅. In addition, we observe one-dimensional-like electronic features from the edges of the cracked ZrTe₅ samples. Our observations indicate that ZrTe₅ is a weak topological insulator and it exhibits a tendency to become a strong topological insulator when the layer distance is reduced.

A topological superconductor (TSC) is a new type of superconductor with non-trivial topology in its bulk electronic structure, which has great potential in both fundamental research and application. However, despite the intensive research efforts worldwide, to date only a few intrinsic (non-heterostructures) materials have been proposed as TSC candidates. In this work, following the theoretical prediction, we experimentally studied a newly proposed TSC candidate, TaSe3. The topological non-trivial surface states were directly observed by using angle-resolved photoemission spectroscopy, while the superconductivity of the compound was examined by both transport and scanning tunneling microscopy measurement. Therefore, TaSe3 was proved to be a promising candidate as a TSC, and a promising research platform for the related novel physics phenomena.