Berlin 2018 – scientific programme

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O: Fachverband Oberflächenphysik

O 113: 2D materials beyond graphene: TMDCs, silicene and relatives V

O 113.4: Talk

Friday, March 16, 2018, 11:15–11:30, MA 043

Strain-induced Formation of Grain Boundaries in the 2D Quantum Spin Hall State in WSe₂ — •Charlotte Herbig¹, Zahra Pedramrazi¹, Madeleine Philips², Dillon Wong¹, Yi Chen¹, Hsin-Zon Tsai¹, Shujie Tang³, Hyejin Ryu⁴, Artem Pulkin⁵, Zahid Hussain⁴, Sung-Kwan Mo⁴, Zhi-Xun Shen³, Oleg Yazyev⁵, Eugene Mele², and Michael F. Crommie¹ — ¹University of California Berkeley — ²University of Pennsylvania — ³Stanford University — ⁴Lawrence Berkeley National Lab — ⁵École Polytechnique Fédérale de Lausanne

Monolayers of group VI transition metal dichalcogenides with chemical formula MX₂, where M stands for Mo or W and X is S, Se, or Te, come in different structural polymorphs such as 1H, 1T, and 1T’. The metastable 1T’ phase of WSe₂ hosts exotic physical properties such as the existence of a 2D topologically non-trivial quantum spin Hall state. The low-symmetry 1T’ phase is structurally degenerate and has three orientation variants. Using the atomically sharp tip of a scanning tunneling microscope, we induce strain on monolayer islands of 1T’-WSe₂ and thereby switch between these three orientations, creating and rearranging grain boundaries between two topologically non-trivial 1T’ phases. The electronic structure of these grain boundaries is then explored via scanning tunneling spectroscopy and compared with calculations of confined electronic modes on the grain boundary.