The critical temperature of smart meta-superconducting MgB2
  Enhancing the critical temperature (TC) is important not only to the practical applications but also to the theories of superconductivity. MgB2 is a type II superconductor with a TC of 39 K, which is very close to the McMillan limit. Improving the TC of MgB2 is challenging but significant. Inspired by the metamaterial structure, we designed a smart meta-superconductor that consists of MgB2 microparticles and Y2O3:Eu3+ nanorods. In the local electric field, Y2O3:Eu3+ nanorods will generate electroluminescence (EL) that can excite MgB2 particles, thereby improving the TC by strengthening the electron-phonon interaction. Each MgB2-based superconductor doped with one of the four dopants of different EL intensities was prepared by an ex-situ process. The results showed that the addition of Y2O3:Eu3+ brings about an impurity effect that decreases the TC and an EL exciting effect that increases the TC. Apart from the EL intensity, the micro-morphology and degree of dispersion of the dopants also affected the TC. This smart meta-superconductor provides a new method for increasing TC. 
Shuo Tao, Yongbo Li, Guowei Chen, Xiaopeng Zhao
cond-mat.supr-con