Distinct multiple fermionic states in a single topological metal*

Among the quantum materials that have recently gained interest are the topological insulators, wherein symmetry-protected surface states cross in reciprocal space, and the Dirac nodal-line semimetals, where bulk bands touch along a line in momentum space. However, the existence of multiple fermion phases in a single material has not been verified yet. Using angle-resolved photoemission spectroscopy (ARPES) and first-principles electronic structure calculations, here we discuss a systematic study of the metallic ternary material discovering properties, which are unique in a single topological quantum material. We experimentally observe weak topological insulator surface states and our calculations suggest the existence of additional strong topological insulator surface states. Our first-principles calculations reveal a one-dimensional Dirac crossing—the surface Dirac-node arc—along a high-symmetry direction, which is confirmed by our ARPES and time-resolved ARPES measurements. Furthermore, we will present our recent results on the experimental observation of new topological quantum materials. These are topological superconductors and magnetic topological materials which were discovered through ARPES and time-resolved ARPES measurements with further support from first-principles calculations.