Topological electronic states in solid materials and the phase transitions between those states have received a great deal of attention as they were the subject of the 2016 Nobel Prize in Physics.

　When the essence of topology (topology) is classified by the characteristics that do not disappear even if it is continuously deformed, such as the number of holes and the number of twists, common properties according to the classification appear regardless of the size and shape of the material. something like.By applying this to the wave function that determines the electronic state, "topological insulators" etc. have been theoretically proposed, and verification by experiments has progressed.However, there has never been a generalized methodology or clear guideline for strategically creating topological materials.

　This time, the international collaborative research group calculated the electronic state of TMD based on the basic principle of quantum mechanics, and theoretically constructed the general principle from it.Then, when experimental verification was performed by angle-resolved photoelectron spectroscopy, which enables direct observation of detailed electronic structures, TMDs with six different compositions were found to have topological surface electronic states and three-dimensional deluxes as theoretically predicted by the proposed general principle. He said that he was able to confirm that the electronic state existed, and succeeded in demonstrating that the general principle is correct.

　This result is expected to give a universal basic theory to the research field of topological electronic materials, and to be an important and new guideline for the control of topological electronic states and material design.

Paper information:[Nature Materials] Ubiquitous formation of bulk Dirac cones and topological surface states from a single orbital manifold in transition-metal dichalcogenides