From local bonding to long-range symmetry-breaking: Polarity, chirality, and the distribution of free carriers in perovskite CsSnBr3
Douglas Fabini a, Kedar Honasoge b, Steffen Klenner c, Mirjam Zipkat d, Le Phuong Hoang b, Jürgen Nuss b, Reinhard Kremer b, Rainer Pöttgen c, Stefan Kaiser b, Bettina Lotsch b
a Department of Chemistry, Massachusetts Institute of Technology (MIT)
b Max Planck Institute for Solid State Research, Heisenbergstraße, 1, Stuttgart, Germany
c Institut für Anorganische und Analytische Chemie, WWU-Münster
d Chemistry Department, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, München 81377, Germany
Proceedings of Online Conference on Atomic-level Characterisation of Hybrid Perovskites (HPATOM2)
Online, Spain, 2022 February 2nd - 3rd
Organizers: Michael Hope and Eve Mozur
Invited Speaker, Douglas Fabini, presentation 015
DOI: https://doi.org/10.29363/nanoge.hpatom.2022.015
Publication date: 30th October 2021

Crystals lacking inversion symmetry have long attracted interest for the properties they can exhibit, from circular dichroism to piezo-, pyro-, and ferro-electricity. Heavy noncentrosymmetric materials displaying Rashba-Dresselhaus effects (momentum-dependent lifting of spin degeneracy via the spin-orbit interaction) are specifically sought as one route to new information processing devices that couple charge and spin. Guided by the chemistry and bonding of Sn(II), we uncover via dielectric and nonlinear optical spectroscopies the previously unstudied polar, chiral ground state phase of perovskite CsSnBr3, which exhibits a bulk Rashba effect. Optical and Mössbauer spectroscopies, X-ray diffraction, and first-principles phonon mode mapping suggest a crystal structure combining octahedral tilting and complex electric dipole order, with unprecedented noncollinear order in two dimensions and ferroic order in the third. 119Sn nuclear magnetic resonance (NMR) spectroscopy and AC transport measurements indicate a complex distribution of free carriers and mobile point defects. We compare the switchabillity of the polarization and spin texture of this phase to the champion bulk Rashba semiconductors and discuss implications for recent claims in other perovskite halides.

D. F. gratefully acknowledges financial support from the Alexander von Humboldt foundation.

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