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Title: Observation of topologically protected states at crystalline phase boundaries in single-layer WSe 2

Transition metal dichalcogenide materials are unique in the wide variety of structural and electronic phases they exhibit in the two-dimensional limit. Here we show how such polymorphic flexibility can be used to achieve topological states at highly ordered phase boundaries in a new quantum spin Hall insulator (QSHI), 1T'-WSe 2. We observe edge states at the crystallographically aligned interface between a quantum spin Hall insulating domain of 1T'-WSe 2 and a semiconducting domain of 1H-WSe 2 in contiguous single layers. The QSHI nature of single-layer 1T'-WSe 2 is verified using angle-resolved photoemission spectroscopy to determine band inversion around a 120 meV energy gap, as well as scanning tunneling spectroscopy to directly image edge-state formation. Using this edge-state geometry we confirm the predicted penetration depth of one-dimensional interface states into the two-dimensional bulk of a QSHI for a well-specified crystallographic direction. In conclusion, these interfaces create opportunities for testing predictions of the microscopic behavior of topologically protected boundary states.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ; ORCiD logo [2] ;  [5] ;  [6] ;  [6] ;  [7] ;  [6] ;  [8] ; ORCiD logo [9] ; ORCiD logo [10] ; ORCiD logo [2] ; ORCiD logo [8]
  1. Donostia International Physics Center (DIPC), San Sebastian (Spain); Centro de Fisica de Materiales (CSIC-UPV/EHU), San Sebastian (Spain); Ikerbasque, Bilbao (Spain)
  2. Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne (Switzerland)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Korea Institute of Science and Technology, Seoul (Korea)
  5. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States); Nanjing Univ., Nanjing (China)
  6. Univ. of California, Berkeley, CA (United States)
  7. Univ. of California, Berkeley, CA (United States); Univ. Autonoma de Madrid, Madrid (Spain)
  8. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  9. SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States)
  10. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Grant/Contract Number:
MAT2017-88377-C2-1-R; AC02-05CH11231; AC02-76SF00515; 306504; EFMA-1542741
Type:
Published Article
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 9; Journal Issue: 1; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE
OSTI Identifier:
1465222
Alternate Identifier(s):
OSTI ID: 1475489; OSTI ID: 1477419

Ugeda, Miguel M., Pulkin, Artem, Tang, Shujie, Ryu, Hyejin, Wu, Quansheng, Zhang, Yi, Wong, Dillon, Pedramrazi, Zahra, Martín-Recio, Ana, Chen, Yi, Wang, Feng, Shen, Zhi -Xun, Mo, Sung -Kwan, Yazyev, Oleg V., and Crommie, Michael F.. Observation of topologically protected states at crystalline phase boundaries in single-layer WSe2. United States: N. p., Web. doi:10.1038/s41467-018-05672-w.
Ugeda, Miguel M., Pulkin, Artem, Tang, Shujie, Ryu, Hyejin, Wu, Quansheng, Zhang, Yi, Wong, Dillon, Pedramrazi, Zahra, Martín-Recio, Ana, Chen, Yi, Wang, Feng, Shen, Zhi -Xun, Mo, Sung -Kwan, Yazyev, Oleg V., & Crommie, Michael F.. Observation of topologically protected states at crystalline phase boundaries in single-layer WSe2. United States. doi:10.1038/s41467-018-05672-w.
Ugeda, Miguel M., Pulkin, Artem, Tang, Shujie, Ryu, Hyejin, Wu, Quansheng, Zhang, Yi, Wong, Dillon, Pedramrazi, Zahra, Martín-Recio, Ana, Chen, Yi, Wang, Feng, Shen, Zhi -Xun, Mo, Sung -Kwan, Yazyev, Oleg V., and Crommie, Michael F.. 2018. "Observation of topologically protected states at crystalline phase boundaries in single-layer WSe2". United States. doi:10.1038/s41467-018-05672-w.
@article{osti_1465222,
title = {Observation of topologically protected states at crystalline phase boundaries in single-layer WSe2},
author = {Ugeda, Miguel M. and Pulkin, Artem and Tang, Shujie and Ryu, Hyejin and Wu, Quansheng and Zhang, Yi and Wong, Dillon and Pedramrazi, Zahra and Martín-Recio, Ana and Chen, Yi and Wang, Feng and Shen, Zhi -Xun and Mo, Sung -Kwan and Yazyev, Oleg V. and Crommie, Michael F.},
abstractNote = {Transition metal dichalcogenide materials are unique in the wide variety of structural and electronic phases they exhibit in the two-dimensional limit. Here we show how such polymorphic flexibility can be used to achieve topological states at highly ordered phase boundaries in a new quantum spin Hall insulator (QSHI), 1T'-WSe2. We observe edge states at the crystallographically aligned interface between a quantum spin Hall insulating domain of 1T'-WSe2 and a semiconducting domain of 1H-WSe2 in contiguous single layers. The QSHI nature of single-layer 1T'-WSe2 is verified using angle-resolved photoemission spectroscopy to determine band inversion around a 120 meV energy gap, as well as scanning tunneling spectroscopy to directly image edge-state formation. Using this edge-state geometry we confirm the predicted penetration depth of one-dimensional interface states into the two-dimensional bulk of a QSHI for a well-specified crystallographic direction. In conclusion, these interfaces create opportunities for testing predictions of the microscopic behavior of topologically protected boundary states.},
doi = {10.1038/s41467-018-05672-w},
journal = {Nature Communications},
number = 1,
volume = 9,
place = {United States},
year = {2018},
month = {8}
}

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