Abstract
Superconductors pose great promise for applications. Over the last century, substantial search efforts failed to find practically valuable, room-temperature superconductors. Meanwhile, the popular Bardeen-Cooper-Schrieffer theory for superconductivity is also facing challenges as it cannot justify the high-temperature superconductors discovered recently. The root problem might be in the traditional model for electrical resistance, suggesting the cause of the resistance is due to particle collision of electron flow in conductors. An alternative theory is proposed in this study. Under pressure, molecules are packed closely. Electron clouds in molecules adjust to adjacent molecules. The uneven distribution of electrons results in compression bonds. So, the distance between molecules may be so small that the valence electrons are close or even at the border between molecules. An electron may drift along borders and switch from one molecule to the next. A series of electron drifts results in a current. The attraction between electrons and nuclei is the primary cause of electrical resistance. To create currents in conductors, energy is needed to lift valence electrons to the borders. The distance between molecules determines the lifting energy, which is proportional to the resistivity. Intermolecular distances result from a balance between intermolecular attraction and repulsion and are also subject to changes in temperature and pressure. Hence, the resistivity of a conductor correlates to the temperature and pressure. For instance, the distance between molecules can be reduced by increasing the confining pressure. This explains why resistivity decreases as pressure increases and high-temperature superconductors are mostly obtained at high pressures. Superconductivity is just a state of matter at certain combinations of temperatures and pressures when the distance between molecules is so small that allows valence electrons to drift from one molecule to the next without the need for lifting energy. Hence, there is no resistance. This theory not only unifies the cause of resistivity for both conductors and superconductors but also superconductivity at low and high temperatures. Based on this theory, a mathematical model has been constructed that predicts and explains the properties and phenomena of superconductivity. Intermolecular repulsion is the primary hurdle to superconductivity. Based on these understandings, promising hints are provided to expedite the search form room-temperature superconductors.
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