Symmetry Dictated Grain Boundary State in a Two-Dimensional Topological Insulator

Hyo Won Kim; Seoung Hun Kang; Hyun Jung Kim; Kisung Chae; Suyeon Cho; Wonhee Ko; Sangjun Jeon; Se Hwang Kang; Heejun Yang; Sung Wng Kim; Seongjun Park; Sungwoo Hwang; Young Kyun Kwon; Young Woo Son

doi:10.1021/acs.nanolett.0c01756

Symmetry Dictated Grain Boundary State in a Two-Dimensional Topological Insulator

Hyo Won Kim, Seoung Hun Kang, Hyun Jung Kim, Kisung Chae, Suyeon Cho, Wonhee Ko, Sangjun Jeon, Se Hwang Kang, Heejun Yang, Sung Wng Kim, Seongjun Park, Sungwoo Hwang, Young Kyun Kwon, Young Woo Son

Research output: Contribution to journal › Article › peer-review

18 Scopus citations

Abstract

Grain boundaries (GBs) are ubiquitous in solids and have been of central importance in understanding the nature of polycrystals. In addition to their classical roles, topological insulators (TIs) offer a chance to realize GBs hosting distinct topological states that can be controlled by their crystal symmetries. However, such roles of crystalline symmetry in two-dimensional (2D) TIs have not been definitively measured yet. Here, we present the first direct evidence of a symmetry-enforced metallic state along a GB in 1T′-MoTe2, a prototypical 2D TI. Using scanning tunneling microscopy, we show a metallic state along a GB with nonsymmorphic lattice symmetry and its absence along another boundary with symmorphic symmetry. Our atomistic simulations demonstrate in-gap Weyl semimetallic states for the former, whereas they demonstrate gapped states for the latter, explaining our observation well. The observed metallic state, tightly linked to its crystal symmetry, can be used to create a stable conducting nanowire inside TIs.

Original language	English
Pages (from-to)	5837-5843
Number of pages	7
Journal	Nano Letters
Volume	20
Issue number	8
DOIs	https://doi.org/10.1021/acs.nanolett.0c01756
State	Published - Aug 12 2020
Externally published	Yes

Funding

We thank the Korea Institute for Advanced Study for providing computing resources (KIAS Center for Advanced Computation Linux Cluster System) for this work. H.-J.K. acknowledges support from the POSCO Science Fellowship of the POSCO TJ Park Foundation. Y.-W.S. was supported by the NRF of Korea (2017R1A5A1014862, SRC program: vdWMRC Center) and by a KIAS individual grant (CG031509).

Funders	Funder number
KIAS	CG031509
POSCO
POSCO TJ Park Foundation
National Research Foundation of Korea	2017R1A5A1014862

Keywords

Grain boundary
Weyl semimetallic states
density functional theory calculations
nonsymmorphic symmetry
scanning tunneling microscopy
topological insulator

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10.1021/acs.nanolett.0c01756

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title = "Symmetry Dictated Grain Boundary State in a Two-Dimensional Topological Insulator",

abstract = "Grain boundaries (GBs) are ubiquitous in solids and have been of central importance in understanding the nature of polycrystals. In addition to their classical roles, topological insulators (TIs) offer a chance to realize GBs hosting distinct topological states that can be controlled by their crystal symmetries. However, such roles of crystalline symmetry in two-dimensional (2D) TIs have not been definitively measured yet. Here, we present the first direct evidence of a symmetry-enforced metallic state along a GB in 1T′-MoTe2, a prototypical 2D TI. Using scanning tunneling microscopy, we show a metallic state along a GB with nonsymmorphic lattice symmetry and its absence along another boundary with symmorphic symmetry. Our atomistic simulations demonstrate in-gap Weyl semimetallic states for the former, whereas they demonstrate gapped states for the latter, explaining our observation well. The observed metallic state, tightly linked to its crystal symmetry, can be used to create a stable conducting nanowire inside TIs.",

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author = "Kim, {Hyo Won} and Kang, {Seoung Hun} and Kim, {Hyun Jung} and Kisung Chae and Suyeon Cho and Wonhee Ko and Sangjun Jeon and Kang, {Se Hwang} and Heejun Yang and Kim, {Sung Wng} and Seongjun Park and Sungwoo Hwang and Kwon, {Young Kyun} and Son, {Young Woo}",

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AU - Cho, Suyeon

AU - Ko, Wonhee

AU - Jeon, Sangjun

AU - Kang, Se Hwang

AU - Yang, Heejun

AU - Kim, Sung Wng

AU - Park, Seongjun

AU - Hwang, Sungwoo

AU - Kwon, Young Kyun

AU - Son, Young Woo

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N2 - Grain boundaries (GBs) are ubiquitous in solids and have been of central importance in understanding the nature of polycrystals. In addition to their classical roles, topological insulators (TIs) offer a chance to realize GBs hosting distinct topological states that can be controlled by their crystal symmetries. However, such roles of crystalline symmetry in two-dimensional (2D) TIs have not been definitively measured yet. Here, we present the first direct evidence of a symmetry-enforced metallic state along a GB in 1T′-MoTe2, a prototypical 2D TI. Using scanning tunneling microscopy, we show a metallic state along a GB with nonsymmorphic lattice symmetry and its absence along another boundary with symmorphic symmetry. Our atomistic simulations demonstrate in-gap Weyl semimetallic states for the former, whereas they demonstrate gapped states for the latter, explaining our observation well. The observed metallic state, tightly linked to its crystal symmetry, can be used to create a stable conducting nanowire inside TIs.

AB - Grain boundaries (GBs) are ubiquitous in solids and have been of central importance in understanding the nature of polycrystals. In addition to their classical roles, topological insulators (TIs) offer a chance to realize GBs hosting distinct topological states that can be controlled by their crystal symmetries. However, such roles of crystalline symmetry in two-dimensional (2D) TIs have not been definitively measured yet. Here, we present the first direct evidence of a symmetry-enforced metallic state along a GB in 1T′-MoTe2, a prototypical 2D TI. Using scanning tunneling microscopy, we show a metallic state along a GB with nonsymmorphic lattice symmetry and its absence along another boundary with symmorphic symmetry. Our atomistic simulations demonstrate in-gap Weyl semimetallic states for the former, whereas they demonstrate gapped states for the latter, explaining our observation well. The observed metallic state, tightly linked to its crystal symmetry, can be used to create a stable conducting nanowire inside TIs.

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Symmetry Dictated Grain Boundary State in a Two-Dimensional Topological Insulator

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