Topological Fermi-arc surface state covered by floating electrons on a two-dimensional electride

Chan-Young Lim; Min-Seok Kim; Dong Cheol Lim; Sunghun Kim; Yeonghoon Lee; Jaehoon Cha; Gyubin Lee; Sang Yong Song; Dinesh Thapa; Jonathan D Denlinger; Seong-Gon Kim; Sung Wng Kim; Jungpil Seo; Yeongkwan Kim

doi:10.1038/s41467-024-49841-6

Topological Fermi-arc surface state covered by floating electrons on a two-dimensional electride

Nat Commun. 2024 Jul 4;15(1):5615. doi: 10.1038/s41467-024-49841-6.

Authors

Chan-Young Lim^#^{1

2}, Min-Seok Kim^#³, Dong Cheol Lim^#^{4

5}, Sunghun Kim^#⁶, Yeonghoon Lee⁷, Jaehoon Cha¹, Gyubin Lee¹, Sang Yong Song³, Dinesh Thapa⁸, Jonathan D Denlinger⁹, Seong-Gon Kim¹⁰, Sung Wng Kim^{11

12}, Jungpil Seo¹³, Yeongkwan Kim¹⁴

Affiliations

¹ Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon, 34141, South Korea.
² Donostia International Physics Center (DIPC), 20018, San Sebastián/Donostia, Spain.
³ Department of Physics and Chemistry, Daegu Gyeongbuk Institute of Science and Technology, Daegu, 42988, South Korea.
⁴ Department of Energy Science, Sungkyunkwan University, Suwon, 16419, South Korea.
⁵ Center for Electride Materials, Sungkyunkwan University, Suwon, 16419, South Korea.
⁶ Department of Physics, Ajou University, Suwon, 16499, South Korea.
⁷ Quantum Spin Team, Korea Research Institute of Standards and Science, Daejeon, 34113, South Korea.
⁸ Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58108, USA.
⁹ Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
¹⁰ Department of Physics & Astronomy and Center for Computational Sciences, Mississippi State University, Mississippi State, MS, 39792, USA. sk162@msstate.edu.
¹¹ Department of Energy Science, Sungkyunkwan University, Suwon, 16419, South Korea. kimsungwng@skku.edu.
¹² Center for Electride Materials, Sungkyunkwan University, Suwon, 16419, South Korea. kimsungwng@skku.edu.
¹³ Department of Physics and Chemistry, Daegu Gyeongbuk Institute of Science and Technology, Daegu, 42988, South Korea. jseo@dgist.ac.kr.
¹⁴ Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon, 34141, South Korea. yeongkwan@kaist.ac.kr.

^# Contributed equally.

Abstract

Two-dimensional electrides can acquire topologically non-trivial phases due to intriguing interplay between the cationic atomic layers and anionic electron layers. However, experimental evidence of topological surface states has yet to be verified. Here, via angle-resolved photoemission spectroscopy (ARPES) and scanning tunnelling microscopy (STM), we probe the magnetic Weyl states of the ferromagnetic electride [Gd₂C]²⁺·2e^-. In particular, the presence of Weyl cones and Fermi-arc states is demonstrated through photon energy-dependent ARPES measurements, agreeing with theoretical band structure calculations. Notably, the STM measurements reveal that the Fermi-arc states exist underneath a floating quantum electron liquid on the top Gd layer, forming double-stacked surface states in a heterostructure. Our work thus not only unveils the non-trivial topology of the [Gd₂C]²⁺·2e^- electride but also realizes a surface heterostructure that can host phenomena distinct from the bulk.

Grants and funding

2022M3H4A1A01010832/National Research Foundation of Korea (NRF)