Ferroelectric domain-wall polarons have been postulated to be responsible for the remarkable optoelectronic properties of soft semiconductors such as hybrid organic-inorganic perovskites [1] and Bi2O2Se [2]. These anisotropic structures are characterized by the formation of a domain wall between two oppositely polarized ferroelectric domains creating a planar channel for electron transport [3]. In this talk, I will present our theoretical results describing these polaron structures within a minimal two-dimensional model of electrons interacting with freely rotating dipoles embedded in the inorganic lattice [4,5]. Based on variational phase diagram analysis, we identify that increasing rotor-electron coupling is the origin of a structural instability. This instability leads to the formation of ferroelectric domain wall polarons via a pseudo-Jahn-Teller symmetry-breaking process. I will discuss how these results are consistent with and generalize computational results on soft semiconductors [6].

[1] K. Miyata and X.-Y. Zhu, Nat. Mater. 17, 379 (2018). DOI: 10.1038/s41563-018-0068-7
[2] F. Wang, W. Chu, L. Huber, T. Tu, Y. Dai, J. Wang, H. Peng, J. Zhao, X. Zhu, Proc. Natl. Acad. Sci. U.S.A. 119 (30) e2122436119, 2022, DOI: 10.1073/pnas.2122436119
[3] F. Wang, Z. Fu, M. E. Ziffer, Y. Dai, S. F. Maehrlein, and X.-Y. Zhu, J. Am. Chem. Soc. 143, 5 (2021). DOI: 10.1021/jacs.0c10943
[4] G. M. Koutentakis, A. Ghazaryan, and M. Lemeshko, Phys. Rev. Research 5, 043016 (2023). DOI: 10.1103/PhysRevResearch.5.043016
[5] F. Kluibenschedl, G. M. Koutentakis, R. Alhyder, M. Lemeshko, arXiv:2407.19993 (2024).
[6] F. Ambrosio, D. Meggiolaro, E. Mosconi, and F. D. Angelis, ACS Energy Lett. 4, 2013 (2019). DOI: 10.1021/acsenergylett.9b01353