Spectroscopic evidence for a type II Weyl semimetallic state in MoTe2

doi:10.1038/nmat4685

Title: Spectroscopic evidence for a type II Weyl semimetallic state in MoTe ₂

In a type I Dirac or Weyl semimetal, the low-energy states are squeezed to a single point in momentum space when the chemical potential μ is tuned precisely to the Dirac/Weyl point. Recently, a type II Weyl semimetal was predicted to exist, where the Weyl states connect hole and electron bands, separated by an indirect gap. This leads to unusual energy states, where hole and electron pockets touch at the Weyl point. Here we present the discovery of a type II topological Weyl semimetal state in pure MoTe ₂, where two sets of Weyl points ( W^±₂ , W^±₃) exist at the touching points of electron and hole pockets and are located at different binding energies above E _F. Using angle-resolved photoemission spectroscopy, modelling, density functional theory and calculations of Berry curvature, we identify the Weyl points and demonstrate that they are connected by different sets of Fermi arcs for each of the two surface terminations. We also find new surface ‘track states’ that form closed loops and are unique to type II Weyl semimetals. Lastly, this material provides an exciting, new platform to study the properties of Weyl fermions.

Authors:

Huang, Lunan ^[1] ; McCormick, Timothy M. ^[2] ; Ochi, Masayuki ^[3] ; Zhao, Zhiying ^[4] ; Suzuki, Michi -To ^[5] ; Arita, Ryotaro ^[6] ; Wu, Yun ^[1] ; ; Cao, Huibo ^[7] ; Yan, Jiaqiang ^[8] ; Trivedi, Nandini ^[2] ; Kaminski, Adam ^[1]

Ames Lab. and Iowa State Univ., Ames, IA (United States)
The Ohio State Univ., Columbus, OH (United States)
Osaka Univ., Osaka (Japan)
Univ. of Tennessee, Knoxville, TN (United States)
RIKEN Center for Emergent Matter Science (CEMS), Saitama (Japan)
RIKEN Center for Emergent Matter Science (CEMS), Saitama (Japan); Tohoku Univ., Miyagi (Japan)
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)

Publication Date:: 2016-07-11

Report Number(s):: IS-J-9004
Journal ID: ISSN 1476-1122; nmat4685

Grant/Contract Number:: AC02-07CH11358; DMR-1420451; NSF-DMR-1309461; 343227

Type:: Accepted Manuscript

Journal Name:: Nature Materials

Additional Journal Information:: Journal Volume: 15; Journal Issue: 11; Journal ID: ISSN 1476-1122

Publisher:: Nature Publishing Group

Research Org:: Ames Laboratory (AMES), Ames, IA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Ames Lab. and Iowa State Univ., Ames, IA (United States); RIKEN Center for Emergent Matter Science (CEMS), Wako (Japan); The Ohio State Univ., Columbus, OH (United States)

Sponsoring Org:: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF); Simons Foundation (United States)

Contributing Orgs:: Osaka Univ. (Japan); Univ. of Tennessee, Knoxville, TN (United States); Tohoku Univ., Sendai (Japan)

Country of Publication:: United States

Language:: English

Subject:: 36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; topological insulators

OSTI Identifier:: 1278751

Alternate Identifier(s):: OSTI ID: 1338564


                    Huang, Lunan, McCormick, Timothy M., Ochi, Masayuki, Zhao, Zhiying, Suzuki, Michi -To, Arita, Ryotaro, Wu, Yun, Mou, Daixiang, Cao, Huibo, Yan, Jiaqiang, Trivedi, Nandini, and Kaminski, Adam. Spectroscopic evidence for a type II Weyl semimetallic state in MoTe2.  United States: N. p.,  
        Web.  doi:10.1038/nmat4685.

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                    Huang, Lunan, McCormick, Timothy M., Ochi, Masayuki, Zhao, Zhiying, Suzuki, Michi -To, Arita, Ryotaro, Wu, Yun, Mou, Daixiang, Cao, Huibo, Yan, Jiaqiang, Trivedi, Nandini, & Kaminski, Adam. Spectroscopic evidence for a type II Weyl semimetallic state in MoTe2.  United States.  doi:10.1038/nmat4685.

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                    Huang, Lunan, McCormick, Timothy M., Ochi, Masayuki, Zhao, Zhiying, Suzuki, Michi -To, Arita, Ryotaro, Wu, Yun, Mou, Daixiang, Cao, Huibo, Yan, Jiaqiang, Trivedi, Nandini, and Kaminski, Adam. 2016.  
        "Spectroscopic evidence for a type II Weyl semimetallic state in MoTe2".  United States.  
        doi:10.1038/nmat4685.  https://www.osti.gov/servlets/purl/1278751.

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@article{osti_1278751,

  title        = {Spectroscopic evidence for a type II Weyl semimetallic state in MoTe2},

  author       = {Huang, Lunan and McCormick, Timothy M. and Ochi, Masayuki and Zhao, Zhiying and Suzuki, Michi -To and Arita, Ryotaro and Wu, Yun and Mou, Daixiang and Cao, Huibo and Yan, Jiaqiang and Trivedi, Nandini and Kaminski, Adam},

  abstractNote = {In a type I Dirac or Weyl semimetal, the low-energy states are squeezed to a single point in momentum space when the chemical potential μ is tuned precisely to the Dirac/Weyl point. Recently, a type II Weyl semimetal was predicted to exist, where the Weyl states connect hole and electron bands, separated by an indirect gap. This leads to unusual energy states, where hole and electron pockets touch at the Weyl point. Here we present the discovery of a type II topological Weyl semimetal state in pure MoTe2, where two sets of Weyl points (W±2 , W±3) exist at the touching points of electron and hole pockets and are located at different binding energies above EF. Using angle-resolved photoemission spectroscopy, modelling, density functional theory and calculations of Berry curvature, we identify the Weyl points and demonstrate that they are connected by different sets of Fermi arcs for each of the two surface terminations. We also find new surface ‘track states’ that form closed loops and are unique to type II Weyl semimetals. Lastly, this material provides an exciting, new platform to study the properties of Weyl fermions.},

  doi          = {10.1038/nmat4685},

  journal      = {Nature Materials},

  number       = 11,

  volume       = 15,

  place        = {United States},

  year         = {2016},

  month        = {7}

}

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10.1038/nmat4685
https://doi.org/10.1038/nmat4685

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Works referenced in this record:

Generalized Gradient Approximation Made Simple
journal, October 1996

Perdew, John P.; Burke, Kieron; Ernzerhof, Matthias
Physical Review Letters, Vol. 77, Issue 18, p. 3865-3868
DOI: 10.1103/PhysRevLett.77.3865

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Hsieh, D.; Qian, D.; Wray, L.
Nature, Vol. 452, Issue 7190, p. 970-974
DOI: 10.1038/nature06843

Tunable vacuum ultraviolet laser based spectrometer for angle resolved photoemission spectroscopy
journal, March 2014

Jiang, Rui; Mou, Daixiang; Wu, Yun
Review of Scientific Instruments, Vol. 85, Issue 3, Article No. 033902
DOI: 10.1063/1.4867517

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Title: Spectroscopic evidence for a type II Weyl semimetallic state in MoTe 2

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Title: Spectroscopic evidence for a type II Weyl semimetallic state in MoTe ₂