Probing ferroelectricity by x-ray absorption spectroscopy in molecular crystals

Abstract

We carry out X-ray absorption spectroscopy experiment at 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 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 are 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.

Organic ferroelectric croconic acid: a concise survey from bulk single crystals to thin films

“…Following the discovery of ferroelectricity in the crystal form of CA, several groups have started working on various aspects of the powder, [48][49][50] bulk single crystal, [51][52][53][54][55][56][57][58][59] self-assembled co-crystal, 60,61 composite film 62 and thin film [63][64][65][66][67][68][69][70] forms of the molecule. Most of the studies have focused on the ferroelectric and optical properties of the macroscopic crystals of CA.…”

Convert Widespread Paraelectric Perovskite to Ferroelectrics

“…DOI: 10.1103/PhysRevLett.128.197601 ABO 3 perovskite is an important family of materials that hosts many intriguing physical properties such as ferroelectricity (FE), ferromagnetism, and multiferroicity [1][2][3][4]. FE is one of the key properties that requires a switchable polar distortion to break the inversion symmetry [5][6][7][8][9]. However, in most perovskites, polarity does not occur independently, but is accompanied or induced by primary structural distortions associated with the oxygen octahedral rotations as in the improper FE [10][11][12][13].…”

Convert widespread paraelectric perovskite to ferroelectrics

“…ABO 3 perovskite is an important family of materials that hosts many intriguing physical properties such as ferroelectricity (FE), ferromagnetism, and multiferroicity [1][2][3][4]. Ferroelectricity is one of the key properties that requires a switchable polar distortion to break the inversion symmetry [5][6][7][8][9]. However, in most perovskites, polarity does not occur independently, but is accompanied or induced by primary structural distortions associated with the oxygen octahedral rotations as in the improper FE [10][11][12][13].…”