Probing ferroelectricity by X-ray absorption spectroscopy in molecular crystals

Authors

Fujie Tang, Temple University
Xuanyuan Jiang, University of Nebraska–Lincoln
Hsin Yu Ko, Princeton University
Jianhang Xu, Temple University
Mehmet Topsakal, Brookhaven National Laboratory
Guanhua Hao, University of Nebraska - LincolnFollow
Alpha T. N'Diaye, Lawrence Berkeley National Laboratory
Peter Dowben, University of Nebraska - LincolnFollow
Deyu Lu, Brookhaven National Laboratory
Xiaoshan Xu, University of Nebraska-LincolnFollow
Xifan Wu, Temple UniversityFollow

Date of this Version

3-1-2020

Citation

PHYSICAL REVIEW MATERIALS 4, 034401 (2020)

DOI: 10.1103/PhysRevMaterials.4.034401

Comments

©2020 American Physical Society. Used by permission.

Abstract

We carry out X-ray absorption spectroscopy experiment at the oxygen K edge in croconic acid (C₅H₂O₅) crystal as a prototype of ferroelectric organic molecular solid, whose electric polarization is generated by proton transfer. The experimental spectrum is well reproduced by the electron-hole excitation theory simulations from configuration generated by ab initio molecular dynamics simulation. When inversion symmetry is broken in the ferroelectric state, the hydrogen bonding environment on the two bonded molecules become inequivalent. Such a difference is sensitively probed by the bound excitation in the pre-edge, which is strongly localized on the excited molecules. Our analysis shows that a satellite peak in the pre-edge will emerge at higher excitation energy, which serves as a clear signature of ferroelectricity in the material.