Abstract
It is very important to elucidate the mechanism of superconductivity for achieving room temperature superconductivity. In the first half of this paper, we give a brief review on mechanisms of superconductivity in many-electron systems. We believe that high-temperature superconductivity may occur in a system with interaction of large-energy scale. Empirically, this is true for superconductors that have been found so far. In the second half of this paper, we discuss cuprate high-temperature superconductors. We argue that superconductivity of high temperature cuprates is induced by the strong on-site Coulomb interaction, that is, the origin of high-temperature superconductivity is the strong electron correlation. We show the results on the ground state of electronic models for high temperature cuprates on the basis of the optimization variational Monte Carlo method. A high-temperature superconducting phase will exist in the strongly correlated region.
Highlights
It is a challenging research subject to clarify the mechanism of high temperature superconductivity, and it has been studied intensively for more than 30 years [1,2,3]
It has been shown that the ground-state energy has a minimum at finite ∆ for the BCS-Gutzwiller wave function with d-wave symmetry in the two-dimensional Hubbard model by using the variational Monte Carlo method [37]
We have discussed the possibility of high temperature superconductivity in many-electron systems
Summary
It is a challenging research subject to clarify the mechanism of high temperature superconductivity, and it has been studied intensively for more than 30 years [1,2,3]. For this purpose, it is important to clarify the ground state and phase diagram of electronic models with strong correlation because high temperature cuprates are strongly correlated electron systems. Many unconventional superconductors that cannot be understood by the BCS theory have been discovered They are, for example, heavy fermion superconductors, organic superconductors and cuprate superconductors for which the pairing mechanism is different from the electron–phonon interaction.
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