期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 114, 期 5, 页码 816-821出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1613110114
关键词
band inversion; Dirac fermions; topological insulators; Landau levels; Zeeman splitting
资金
- Hundred Talents Program of Chinese Academy of Sciences
- National Key Research and Development Program of China [2016YFA0300600]
- European Research Council (ERC ARG MOMB Grant) [320590]
- National Science Foundation of China [11120101003, 11327806]
- 973 project of the Ministry of Science and Technology of China [2012CB821403]
- National Science Foundation [DMR-1157490]
- State of Florida
- Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, US Department of Energy [DE-SC00112704]
- European Research Council (ERC) [320590] Funding Source: European Research Council (ERC)
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, ZrTe5, was theoretically predicted to be a TI. Here, we report an infrared transmission study of a high-mobility [similar to 33,000 cm(2)/(V.s)] multilayer ZrTe5 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 similar to 10 meV and a root 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. Our results not only provide spectroscopic evidence for the TI state in ZrTe5 but also open up a new avenue for fundamental studies of Dirac fermions in van der Waals materials.
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