The Development of Organic Conductors: Organic Superconductors
نویسنده
چکیده
Superconductivity ( a new state of matter) has been one of the major discovery of the twentieth century in physics. From an experimental point of view the finding by Kamerlingh Onnes[1] in 1911 of a current travelling without resistance through a metal cooled at very low temperature paved the way to a very large number of industrial applications. And this, long before the proposal of a satisfactory theoretical framework by Bardeen, Cooper and Schrieffer (BCS)[2] in 1957 explaining both the zero resistance state and the magnetic flux expulsion ( the Meissner effect). Furthermore, the BCS theory has also been the paradigm of modern physical theories based on the importance of the quantum nature at low temperature since it relies on the establishment of a new long range ordered state. BCS emphasized the existence of a two body attractive interaction between charge carriers (either electrons or holes) being a prerequisite for a Bose condensation of electron pairs into the superconducting state. This net attractive coupling in spite of the Coulomb repulsion between carriers of the same sign relies closely on an attraction between electrons mediated by their interaction with excitations of the lattice namely, the phonons. Consequently, a major achievement of the BCS theory has been the understanding of the ionic mass dependent of the critical temperature i.e. (Tc αM−1/2). Although Fröhlich had proposed earlier in 1954 a model for superconductivity based on the involvement of the lattice [3] this theory were unable to account for the superconductivity of metals but turned out to be quite relevant later for the interpretation of the transport properties in some one dimensional organic compounds, vide infra. At the beginning of the 60’s searching for new materials exhibiting the highest possible values of superconducting tc was already
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