Distinct multiple fermionic states in a single topological metal

• Published in: Nature communications Vol. 9; no. 1; pp. 3002 - 8
• Main Authors: Hosen, M. Mofazzel, Dimitri, Klauss, Nandy, Ashis K., Aperis, Alex, Sankar, Raman, Dhakal, Gyanendra, Maldonado, Pablo, Kabir, Firoza, Sims, Christopher, Chou, Fangcheng, Kaczorowski, Dariusz, Durakiewicz, Tomasz, Oppeneer, Peter M., Neupane, Madhab
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-08-2018; Nature Publishing Group; Nature Portfolio
• Subjects: 140/146; 639/301/119/2792/4128; 639/766/119/995; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Electronic structure; First principles; Humanities and Social Sciences; Mathematical analysis; Metalloids; multidisciplinary; Photoelectric emission; Quantum theory; Science; Science (multidisciplinary); Spectroscopy; Symmetry; Topological insulators
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-05233-1

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 k-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, we systematically study the metallic material Hf
2
Te
2
P and discover properties, which are unique in a single topological quantum material. We experimentally observe weak topological insulator surface states and our calculations suggest 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 measurements. This novel state originates from the surface bands of a weak topological insulator and is therefore distinct from the well-known Fermi arcs in semimetals.
The existence of multiple topological phases in a single material, although theoretically possible, has not been verified. Here, the authors observe weak topological insulator surface states and a one-dimensional Dirac-node crossing surface state in a single metallic material Hf
2
Te
2
P.