Effective rotor lattice model for ferroelectric domain-wall polarons in two dimensions

Ferroelectric domain-wall polarons are postulated to be responsible for the remarkable optoelectronic properties of soft semiconductors such as hybrid organic-inorganic perovskites [1]. In the direction of the domain walls, the rotors are polarized in opposite directions, which causes the electron to localize along one axis of the lattice [2]. Here, we present a theoretical description of these polarons within a minimal two-dimensional model of electrons interacting with freely rotating dipoles embedded in the inorganic lattice. Based on a variational phase diagram analysis, we identify the rotor-electron coupling as the origin of a structural instability, which leads to the formation of the domain walls via a pseudo-Jahn-Teller symmetry-breaking process. These results agree with and generalize computational results on soft semiconductors [3].

[1] Miyata, K., Zhu, XY. Nature Mater 17, 379–381 (2018). DOI: 10.1038/s41563-018-0068-7

[2] F. Wang, Y. Fu, M. E. Ziffer, Y. Dai, S. F. Maehrlein, and X.-Y. Zhu. Journal of the American Chemical Society 2021 143 (1), 5-16. DOI: 10.1021/jacs.0c10943

[3] F. Ambrosio, D. Meggiolaro, E. Mosconi, F. D. Angelis. ACS Energy Lett. 2019, 4, 8, 2013–2020. DOI: 10.1021/acsenergylett.9b01353