Comprehensive review on Froehlich entropy estimation: a technique to investigate the state of order in condensed matter

Abstract: The so-called Froehlich entropy is the entropy variation of a material under the application of an electric field. This quantity can be calculated, under suitable hypotheses, directly from the measured real part of the dielectric function. Although Froehlich entropy is defined for a biased sample, a straightforward physical interpretation correlates it to the state of order of the considered physical system in absence of field. When Froehlich entropy is calculated from experimental results, its trend is able to give several information about the evolution in temperature of the explored compound, especially of its phase transition features. We here provide a comprehensive review of the physical systems (dipolar liquids and nematicons, organic molecular crystals, metallic nanoparticles, inorganic disordered ferroelectrics, etc.) where this approach has been exploited with the aim of evaluating their state of order. The variety of compounds where this method has been applied demonstrates that the estimation of the Froehlich entropy can be considered a trustworthy tool for carrying out study on the state of order of different classes of materials. Indeed Froehlich entropy evaluation can be considered a fruitful and reliable investigation technique which can be exploited alongside more usual experimental approaches.