Magneic-field-enhanced superconductivity

“磁场增强超导性”=MFES，即临界磁场随温度升高而增加的超导状态分为两类。对于Al和TiN薄膜，在平行磁场下，上下自旋的无带隙能谱的自旋顺磁分裂导致高熵超导态，并在较高温度下驱动超导态。另一种是在Au和Ge的叠层薄膜界面处形成的二维薄膜超导体。在零场临界温度以上的磁场作用下，超导态出现，根据热力学，前者是熵驱动超导态（EDS），后者是顺磁驱动超导态（PDS）。对于后者，其产生机制至今尚未完全确定，边界散射并不是薄膜产生PDS的原因。从临界场的温度依赖性分析可知，PDS的最合理机制是由于金属-绝缘体转变附近的电子局域化和超导性之间的竞争，即超薄膜中的强局域化是导致PDS出现的原因。为了更好地理解PDS的机理，需要建立包括电子-电子相互作用的金属-绝缘体转变附近的超导理论。

"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.