利用界面效應提高超導溫度

Abstract

近年關於兩種不同超導材料其界面處的新穎，超導性已經受到關注。這種變化使我們有機會突破當前高溫超導體的限制。延續我們團隊先前對LSCO薄膜的研究，我們已成功通過脈衝激光沉積製造的La2-xSrxCuO4（0≤x≤0.4）雙層薄膜，且利用這組合上層為La2-xSrxCuO4(x=0.3)下層為 La2-xSrxCuO4(x=0.2, Tc=30 K)的界面。此雙層薄膜超導溫度為32 K，成功證實雙層薄膜在界面處確實能有效提升超導溫度。 接著我們通過控制雙層薄膜厚度和摻雜濃度的各種組合進行更完整與系統性的分析，以期將這界面效應最佳化，結果我們成功完成Tc=43 K的LSCO雙層薄膜，此超導溫度已超過此材料在bulk和在氧氣環境下成長的LSCO薄膜的最高超導溫度。接著我們嘗試三種方法分別為控氧、基板處理、增加同質層使雙層薄膜的品質有很大的提升。

The recent research about the enhancement of superconductivity at the interface of two different superconducting materials has received much attention. This approach gives us the opportunity to break through the limits of current Tc in high-temperature superconductors. Following our previous study of LSCO thin films, we studied the enhancement of the superconducting transition temperature at the interface of La2-xSrxCuO4 (0≤x≤0.4) bilayer thin films, which were fabricated by pulsed laser deposition. With the upper layer of La2-xSrxCuO4 (x=0.3) and of bottom layer La2-xSrxCuO4(x=0.2, Tc=30 K), we found that the Tc of this bilayer is up to 32 K. This result indicates that we succeeded in proving the effective enhancement of the superconducting transition temperature at the interface of bilayer thin films. In this work, we further conducted more complete and systematic analysis by controlling bilayers with different combination of film thicknesses and doping concentration, to optimize the interface and diffusion effects in La2-xSrxCuO4 system. We succeed in fabricating LSCO bilayer thin films, whose Tc is up to 43 K. This temperature is beyond the Tc of the same films under growth environment of oxygen. Later we have tried three methods to improve the quality of bilayer thin films, which are annealing in oxygen, substrate treatment and the introduction of a homolayer.