Optical effects of small polarons at high frequencies with an application to reduced strontiumtitanate

Abstract

Theoretical expressions for the complex electrical conductivity of small polarons are given for frequencies co~, where ~ is an average frequency of the optical phonons. In this frequency range the complex conductivity is independent of the temperature.As an application an analysis is carried out of optical and d.c. data for reduced SrTiO 3. It is shown that a consistent interpretation of these data as well with respect to their absolute magnitude as well with respect to their frequency dependence is possible in terms of the small polaron picture.

Optical absorption and single-particle excitations in the two-dimensional Holsteint−Jmodel

“…Most notably, we are able to reproduce the experimentally observed asymmetry in the shape of the spectrum, in particular the very gradual decay of σ reg (ω) at high energies. It is worth mentioning that this behaviour cannot be obtained from a simple fit to the analytical expressions derived for the small polaron hopping conductivity [67,68,16]. Exploiting the f-sum rule we found that there are almost no contributions from band-like carriers in agreement with the experimental findings [16,18].…”

Many-body large polaron optical conductivity inSrTi1−xNbxO3

“…Previous optical measurements on strontium titanate were interpreted in terms of small polarons [26,28]. However, that assumption contradicts the interpretation of transport measurements [29], which rather support the large-polaron picture.…”

“…[33][34][35][36]. The same problem for the small polaron was investigated in [28,37]. In the large-polaron theory, the optical absorption is provided by transitions (with 0, 1, .…”

High temperature far-infrared dynamics of orthorhombic NdMnO3: emissivity and reflectivity

“…[27] We assume that frequency dependent conductivities result from the addition of gaussian-like (eq. 9) individual contributions, each of them, calculated at a phonon frequency ϖ j .…”