Emergence of Improper Electronic Ferroelectricity and Flat Band in Twisted Bilayer Tl₂S

Gui, Zhigang1,2; Li, Wei3; Huang, Li1,2,4

2024-02-28

10.1021/acs.nanolett.4c00141

NANO LETTERS   影响因子和分区

1530-6984

1530-6992

Two-dimensional (2D) ferroelectrics possessing out-of-plane (OP) polarization are highly desirable for applications and fundamental physics. Here, by first-principles calculations, we reveal that large-angle interlayer twisting can efficiently stabilize an unexpected ordering of sizable electric dipoles, producing OP polarization out of the centrosymmetric ground-state structure of Tl2S, in great contrast to the recently proposed interlayer-sliding ferroelectricity. The ferroelectricity originates from a nonlinear coupling between a polar order dominantly contributed by electrons and an unstable phonon mode associated with a commensurate k point (1/3, 1/3, 0) in the two constituent monolayers, therefore indicating an improper and electronic ferroelectric nature. More interestingly, a flat band and a van Hove singularity occur in its electronic structures just below the Fermi level in the large-angle twisted bilayer Tl2S. The unusual coexistence of improper electronic ferroelectricity, a flat band, and a van Hove singularity in one 2D material offers exceptional opportunities for exploring novel physics and applications.

2D materials improper ferroelectricity electronicferroelectricity flat band

SCI ; EI

英语

第一 ; 通讯

Ministry of Science and Technology of the People's Republic of China[2022YFA1402903] ; Ministry of Science and Technology of the People's Republic of China["12004160","12374059"] ; National Natural Science Foundation of China[KQTD20190929173815000] ; Shenzhen Science and Technology Program[2019ZT08C044] ; Guangdong Innovative and Entrepreneurial Research Team Program[20210087DR] ; Laboratory Directed Research and Development Program of Los Alamos National Laboratory (LANL)[89233218CNA000001] ; Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area (Guangdong)[2022B1212010008]

Chemistry ; Science & Technology - Other Topics ; Materials Science ; Physics

Chemistry, Multidisciplinary ; Chemistry, Physical ; Nanoscience & Nanotechnology ; Materials Science, Multidisciplinary ; Physics, Applied ; Physics, Condensed Matter

WOS:001176768800001

AMER CHEMICAL SOC

MATERIALS SCIENCE

Web of Science

1.Southern Univ Sci & Technol, Dept Phys, Shenzhen 518055, Guangdong, Peoples R China
2.Southern Univ Sci & Technol, Acad Adv Interdisciplinary Studies, Shenzhen 518055, Guangdong, Peoples R China
3.Los Alamos Natl Lab, Comp Computat & Stat Sci Div, Los Alamos, NM 87545 USA
4.Quantum Sci Ctr Guangdong Hong Kong Macao Greater, Hong Kong 518045, Peoples R China

Gui, Zhigang,Li, Wei,Huang, Li. Emergence of Improper Electronic Ferroelectricity and Flat Band in Twisted Bilayer Tl₂S[J]. NANO LETTERS,2024,24(10).

Gui, Zhigang,Li, Wei,&Huang, Li.(2024).Emergence of Improper Electronic Ferroelectricity and Flat Band in Twisted Bilayer Tl₂S.NANO LETTERS,24(10).

Gui, Zhigang,et al."Emergence of Improper Electronic Ferroelectricity and Flat Band in Twisted Bilayer Tl₂S".NANO LETTERS 24.10(2024).