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Title: Spectroscopic evidence for bulk-band inversion and three-dimensional massive Dirac fermions in ZrTe 5

Three-dimensional topological insulators (3D TIs) represent states of quantum matters in which surface states are protected by time-reversal symmetry and an inversion occurs between bulk conduction and valence bands. However, the bulk-band inversion, which is intimately tied to the topologically nontrivial nature of 3D Tis, has rarely been investigated by experiments. Besides, 3D massive Dirac fermions with nearly linear band dispersions were seldom observed in TIs. Recently, a van der Waals crystal, ZrTe 5, was theoretically predicted to be a TI. Here, we report an infrared transmission study of a high-mobility [~33,000 cm 2/(V • s)] multilayer ZrTe 5 flake at magnetic fields (B) up to 35 T. Our observation of a linear relationship between the zero-magnetic-field optical absorption and the photon energy, a bandgap of ~10 meV and a √B dependence of the Landau level (LL) transition energies at low magnetic fields demonstrates 3D massive Dirac fermions with nearly linear band dispersions in this system. More importantly, the reemergence of the intra-LL transitions at magnetic fields higher than 17 T reveals the energy cross between the two zeroth LLs, which reflects the inversion between the bulk conduction and valence bands. Finally, our results not only provide spectroscopic evidence formore » the TI state in ZrTe 5 but also open up a new avenue for fundamental studies of Dirac fermions in van der Waals materials.« less
Authors:
 [1] ;  [2] ;  [3] ;  [3] ;  [3] ;  [3] ;  [4] ;  [5] ; ORCiD logo [3] ;  [3] ;  [6]
  1. Chinese Academy of Sciences (CAS), Beijing (China)
  2. Peking Univ., Beijing (China)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States)
  4. Chinese Academy of Sciences (CAS), Beijing (China); Delft Univ. of Technology, Delft (The Netherlands)
  5. Wuhan Univ., Wuhan (China)
  6. Peking Univ., Beijing (China); Collaborative Innovation Center of Quantum Matter, Beijing (China)
Publication Date:
Report Number(s):
BNL-113757-2017-JA
Journal ID: ISSN 0027-8424; R&D Project: PO010; KC0201060
Grant/Contract Number:
SC00112704
Type:
Accepted Manuscript
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 114; Journal Issue: 5; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; band inversion; Dirac fermions; topological insulators; Landau levels; Zeeman splitting
OSTI Identifier:
1354629