Magneic-field-enhanced superconductivity

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"Magnetic-Field-Enhanced Superconducutivity" =MFES,namely, the superconducting state whose critical magnetic field is increased with increasing temperature is classified in the two categories. One is found for thin films of Al and TiN under parallel magnetic fields that the spin paramagnetic splitting of the gapless energy spectra for up and down spings indued high entropy superconducting state and has driven a supercondcuting state at higher temperatures. The other was found for the two dimensional thin film superconductors which was formed at the interface of stacked thin films of Au and Ge. In this case, superconducting state appears above the zero field critical temperature under magnetic fields.According to themodynamics, the former is the entropy driven superconducting stage (EDS) and the latter is a paramagnetically driven superconducting state (PDS). For the latter, the the mechanism of this PDS is not settled so far.The boundary scattering does not cause the PDS for thin films. The most plausible mechanism for PDS is considered to be due to the competition between the electron localization and superconductivity near the metal-insulator transition, that is, the strong localization in ultra thin films is considered to be responsible for the appearance of the PDS from the analysis of the temperature dependence of critical field. Theory of superconductivity near the metal-insulator transition including electron-electron interaction is desired to be established for understanding the mcchanism of PDS.