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arXiv · 2603.21994

In-plane and out-of-plane electric dipoles and phase transitions in 2D-layered TlGaS2

A. D. Molchanova·L. H. Yin·L. P. Gao·W. H. Song·Y. P. Sun·K. R. Allahverdiyev·M. N. Popova
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Abstract

Out-of-plane and in-plane electric polarization, which rarely coexist in a two-dimensional (2D) ferroelectric material, offer different advantages in ferroelectricity-based devices. Here, we report the coexistence of in-plane and out-of-plane electric dipoles, along with various phase transitions, in 2D van der Waals layered TlGaS2 single crystal. Quantum paraelectricity was observed along both in-plane and out-of-plane directions of the TlGaS2 crystal. Detailed investigation of the quantum paraelectric soft-mode behavior reveals a close correlation between the electric dipoles and the off-center displacement of Tl1+ ions with 6s2 lone pairs in TlGaS2. Anomalies near temperatures of about 120 K and 60-75 K in dielectric and/or infrared spectra indicate the existence of local or weak long-range structural transitions in TlGaS2. Our results provide important experimental evidence for elucidating the phase transitions and coexistence of in-plane and out-of-plane electric dipoles in 2D layered TlGaS2.

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A. D. Molchanova, L. H. Yin, L. P. Gao, W. H. Song, Y. P. Sun, K. R. Allahverdiyev, M. N. Popova. 2026-03-23. In-plane and out-of-plane electric dipoles and phase transitions in 2D-layered TlGaS2. https://doi.org/10.1103/82bg-5mt2

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