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Title: Observation of unusual topological surface states in half-Heusler compounds LnPtBi (Ln=Lu, Y)

Abstract

Topological quantum materials represent a new class of matter with both exotic physical phenomena and novel application potentials. Many Heusler compounds, which exhibit rich emergent properties such as unusual magnetism, superconductivity and heavy fermion behaviour, have been predicted to host non-trivial topological electronic structures. The coexistence of topological order and other unusual properties makes Heusler materials ideal platform to search for new topological quantum phases (such as quantum anomalous Hall insulator and topological superconductor). By carrying out angle-resolved photoemission spectroscopy and ab initio calculations on rare-earth half-Heusler compounds LnPtBi (Ln=Lu, Y), we directly observe the unusual topological surface states on these materials, establishing them as first members with non-trivial topological electronic structure in this class of materials. Moreover, as LnPtBi compounds are non-centrosymmetric superconductors, our discovery further highlights them as promising candidates of topological superconductors.

Authors:
 [1];  [2];  [3];  [3];  [1];  [4]; ORCiD logo [5];  [5];  [5];  [6];  [3];  [7]
  1. Chinese Academy of Sciences (CAS), Shanghai (China). Shanghai Inst. of Ceramics, Key Lab. for Energy-Conversion Materials
  2. Tsinghua Univ., Beijing (China)
  3. Max Planck Society, Dresden (Germany). Max Planck Inst. for the Physics of Complex Systems
  4. Chinese Academy of Sciences (CAS), Beijing (China)
  5. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)
  6. Chinese Academy of Sciences (CAS), Shanghai (China). Shanghai Inst. of Ceramics, Key Lab. for Energy-Conversion Materials; Max Planck Society, Dresden (Germany). Max Planck Inst. for the Physics of Complex Systems
  7. Chinese Academy of Sciences (CAS), Shanghai (China). Shanghai Inst. of Ceramics, Key Lab. for Energy-Conversion Materials; Tsinghua Univ., Beijing (China)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1377502
Grant/Contract Number:
AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 7; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; electronic properties and materials; topological insulators

Citation Formats

Liu, Z. K., Yang, L. X., Wu, S. -C., Shekhar, C., Jiang, J., Yang, H. F., Zhang, Y., Mo, S. -K., Hussain, Z., Yan, B., Felser, C., and Chen, Y. L.. Observation of unusual topological surface states in half-Heusler compounds LnPtBi (Ln=Lu, Y). United States: N. p., 2016. Web. doi:10.1038/ncomms12924.
Liu, Z. K., Yang, L. X., Wu, S. -C., Shekhar, C., Jiang, J., Yang, H. F., Zhang, Y., Mo, S. -K., Hussain, Z., Yan, B., Felser, C., & Chen, Y. L.. Observation of unusual topological surface states in half-Heusler compounds LnPtBi (Ln=Lu, Y). United States. doi:10.1038/ncomms12924.
Liu, Z. K., Yang, L. X., Wu, S. -C., Shekhar, C., Jiang, J., Yang, H. F., Zhang, Y., Mo, S. -K., Hussain, Z., Yan, B., Felser, C., and Chen, Y. L.. 2016. "Observation of unusual topological surface states in half-Heusler compounds LnPtBi (Ln=Lu, Y)". United States. doi:10.1038/ncomms12924. https://www.osti.gov/servlets/purl/1377502.
@article{osti_1377502,
title = {Observation of unusual topological surface states in half-Heusler compounds LnPtBi (Ln=Lu, Y)},
author = {Liu, Z. K. and Yang, L. X. and Wu, S. -C. and Shekhar, C. and Jiang, J. and Yang, H. F. and Zhang, Y. and Mo, S. -K. and Hussain, Z. and Yan, B. and Felser, C. and Chen, Y. L.},
abstractNote = {Topological quantum materials represent a new class of matter with both exotic physical phenomena and novel application potentials. Many Heusler compounds, which exhibit rich emergent properties such as unusual magnetism, superconductivity and heavy fermion behaviour, have been predicted to host non-trivial topological electronic structures. The coexistence of topological order and other unusual properties makes Heusler materials ideal platform to search for new topological quantum phases (such as quantum anomalous Hall insulator and topological superconductor). By carrying out angle-resolved photoemission spectroscopy and ab initio calculations on rare-earth half-Heusler compounds LnPtBi (Ln=Lu, Y), we directly observe the unusual topological surface states on these materials, establishing them as first members with non-trivial topological electronic structure in this class of materials. Moreover, as LnPtBi compounds are non-centrosymmetric superconductors, our discovery further highlights them as promising candidates of topological superconductors.},
doi = {10.1038/ncomms12924},
journal = {Nature Communications},
number = ,
volume = 7,
place = {United States},
year = 2016,
month = 9
}

Journal Article:
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  • Using rst-principles calculations within density functional theory, we explore the feasibility of converting ternary half-Heusler compounds into a new class of three-dimensional topological insu- lators (3DTI). We demonstrate that the electronic structure of unstrained LaPtBi as a prototype system exhibits distinct band-inversion feature. The 3DTI phase is realized by applying a uni- axial strain along the [001] direction, which opens a bandgap while preserving the inverted band order. A denitive proof of the strained LaPtBi as a 3DTI is provided by directly calculating the topological Z2 invariants in systems without inversion symmetry. We discuss the implications of the present studymore » to other half-Heusler compounds as 3DTI, which, together with the magnetic and superconducting properties of these materials, may provide a rich platform for novel quantum phenomena.« less
  • Topological semimetals (TSMs) including Weyl semimetals and nodal-line semimetals are expected to open the next frontier of condensed matter and materials science. Although the first inversion breaking Weyl semimetal was recently discovered in TaAs, its magnetic counterparts, i.e., the time-reversal breaking Weyl and nodal line semimetals, remain elusive. They are predicted to exhibit exotic properties distinct from the inversion breaking TSMs including TaAs. In this paper, we identify the magnetic topological semimetal states in the ferromagnetic half-metal compounds Co 2TiX (X = Si, Ge, or Sn) with Curie temperatures higher than 350 K. Our first-principles band structure calculations show that,more » in the absence of spin-orbit coupling, Co 2TiX features three topological nodal lines. The inclusion of spin-orbit coupling gives rise to Weyl nodes, whose momentum space locations can be controlled as a function of the magnetization direction. Lastly, our results not only open the door for the experimental realization of topological semimetal states in magnetic materials at room temperature, but also suggest potential applications such as unusual anomalous Hall effect in engineered monolayers of the Co 2TiX compounds at high temperature.« less
  • Angle resolved photoemission spectroscopy (ARPES) study on TlBiTe2 and TlBiSe2 from a Thallium-based III-V-VI2 ternary chalcogenides family revealed a single surface Dirac cone at the center of the Brillouin zone for both compounds. For TlBiSe{sub 2}, the large bulk gap ({approx} 200meV) makes it a topological insulator with better mechanical properties than the previous binary 3D topological insualtor family. For TlBiTe{sub 2}, the observed negative bulk gap indicates it as a semi-metal, rather than a narrow gap semi-conductor as conventionally believed; this semi-metality naturally explains its mysteriously small thermoelectric figure of merit comparing to other compounds in the family. Finally,more » the unique band structures of TlBiTe{sub 2} also suggests it as a candidate for topological superconductors.« less
  • The discovery of topological insulators, materials with bulk band gaps and protected cross-gap surface states in compounds such as Bi 2Se 3, has generated much interest in identifying topological surface states (TSSs) in other classes of materials. In particular, recent theoretical calculations suggest that TSSs may be found in half-Heusler ternary compounds. If experimentally realizable, this would provide a materials platform for entirely new heterostructure spintronic devices that make use of the structurally identical but electronically varied nature of Heusler compounds. Here we show the presence of a TSS in epitaxially grown thin films of the half-Heusler compound PtLuSb. Spin-more » and angle-resolved photoemission spectroscopy, complemented by theoretical calculations, reveals a surface state with linear dispersion and a helical tangential spin texture consistent with previous predictions. As a result, this experimental verification of topological behavior is a significant step forward in establishing half-Heusler compounds as a viable material system for future spintronic devices.« less
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