A review of recent progress in understanding the spontelectric state of matter

Abstract

The spontelectric state of matter is exemplified by the presence of static, spontaneous electric fields extending throughout thin films of dipolar solids. The spontelectric state was discovered using a low energy electron beam technique. Following a resume of the characteristics and of a model for the spontelectric effect, a description is given of the counter-intuitive behaviour of fields in films of methyl formate as a function of deposition temperature, T. It is found that films for T  77.5K show the expected decrease in the field with increasing T but, for T ≥ 77.5K, an increase in the field for higher T is revealed. Analysis of these results illustrates the non-linear characteristics of the spontelectric state. Recently it has been shown that Reflection-Absorption Infrared Spectroscopy (RAIRS) provides a new and independent technique for the detection of the spontelectric effect, through the observation of vibrational Stark shifts in spectra of films. Stark shifts for nitrous oxide are demonstrated to be in harmony with electric fields measured using the electron beam technique. The method is then applied to carbon monoxide, showing that this material displays the spontelectric effect between deposition temperatures of 20K and 26K.

Absorption by Spinning Dust: A Contaminant for High-redshift 21 cm Observations

“…Polarized ice mantles: ices deposited on grains can also be spontaneously polarized (Field et al 2013;Plekan et al 2017) by either the substrate itself or the electric field if the grain is charged. This polarization can extend through hundreds of monolayers, but the observed net polarization per dipole is only a few percent of the intrinsic dipole moment per molecule.…”

Non-linear and non-local behaviour in spontaneously electrical solids

“…The onset of crystallization of MF has been reported for temperatures between 90 and 100 K in transmission 15 and in RAIR spectra 16 , signalled by sharpening of the absorption lines above 90 to 100 K. Mutual polarization in the solid also leads to a strong decrease in the effective dipole moment compared with the gas phase, via µ = µ 0 /(1+k/s 3 ), where s is the average spacing between successive layers,  is the molecular polarizability, k = 11.034 and  0 is the gas phase dipole moment of the molecules involved. For cis-MF, s = 0.244 nm,  = 5.25  10 -30 m 3 ,  0 = 0.6949 au (or 1.766 D), giving  = 0.354 D. 2,3 Fitting data for deposition temperatures between 55 and 75K to equations (1) and (2), yields <E sym > = 1.206 × 10 7 V m -1 , <E asym > = 1.148 × 10 9 V m -1 ,  = 1.45 × 10 4 . These values then go on to predict the observed qualitatively distinctive rise in the spontelectric field for deposition temperatures above 75 K, as seen in Figure 1 and in Table 1 for < z >/.…”

Wannier-Mott Excitons in Nanoscale Molecular Ices

“…Here we expand the diversity of materials showing Wannier-Mott excitons in a very simple species, unexpectedly finding these excitons in solid CO, which is both a high band gap material (>8 eV) and of low electrical permittivity. The presence of Wannier-Mott excitons in solid CO may be identified through the spontelectric nature of thin films of dipolar materials [8][9][10][11][12], where the spontaneous polarization charge and the accompanying spontelectric field are generated through dipole orientation. Note that spontelectrics are radically different from ferroelectric species [13,14], in which spontaneous polarization results from a crystallographic phenomenon based on individual unit cells, whereas spontelectric polarization is due to a collective, long-range interaction extending throughout the film [9].…”