Observation of topologically protected states at crystalline phase boundaries in single-layer WSe2

Miguel M Ugeda; Artem Pulkin; Shujie Tang; Hyejin Ryu; Quansheng Wu; Yi Zhang; Dillon Wong; Zahra Pedramrazi; Ana Martín-Recio; Yi Chen; Feng Wang; Zhi-Xun Shen; Sung-Kwan Mo; Oleg V Yazyev; Michael F Crommie

doi:10.1038/s41467-018-05672-w

Observation of topologically protected states at crystalline phase boundaries in single-layer WSe₂

Nat Commun. 2018 Aug 24;9(1):3401. doi: 10.1038/s41467-018-05672-w.

Authors

Miguel M Ugeda^{1

2

3}, Artem Pulkin⁴, Shujie Tang^{5

6}, Hyejin Ryu^{5

7}, Quansheng Wu^{4

8}, Yi Zhang^{5

6

9}, Dillon Wong¹⁰, Zahra Pedramrazi¹⁰, Ana Martín-Recio^{10

11}, Yi Chen¹⁰, Feng Wang^{10

12

13}, Zhi-Xun Shen^{6

14}, Sung-Kwan Mo⁵, Oleg V Yazyev^{4

8}, Michael F Crommie^{15

16

17}

Affiliations

¹ Donostia International Physics Center (DIPC), Manuel Lardizábal 4, 20018, San Sebastián, Spain. [email protected].
² Centro de Física de Materiales (CSIC-UPV/EHU), Manuel Lardizábal 5, 20018, San Sebastián, Spain. [email protected].
³ Ikerbasque, Basque Foundation for Science, 48013, Bilbao, Spain. [email protected].
⁴ Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland.
⁵ Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
⁶ Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA.
⁷ Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, Korea.
⁸ National Centre for Computational Design and Discovery of Novel Materials MARVEL, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland.
⁹ National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
¹⁰ Department of Physics, University of California at Berkeley, Berkeley, CA, 94720, USA.
¹¹ Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049, Madrid, Spain.
¹² Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
¹³ Kavli Energy NanoScience Institute at the University of California Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
¹⁴ Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA, 94305, USA.
¹⁵ Department of Physics, University of California at Berkeley, Berkeley, CA, 94720, USA. [email protected].
¹⁶ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA. [email protected].
¹⁷ Kavli Energy NanoScience Institute at the University of California Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA. [email protected].

Abstract

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. These interfaces create opportunities for testing predictions of the microscopic behavior of topologically protected boundary states.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

Abstract

Publication types

Grants and funding