WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
Nat Nanotechnol. 2011 May 22;6(7):408-12. doi: 10.1038/nnano.2011.78.
Superconductivity at interfaces has been investigated since the first demonstration of electric-field-tunable superconductivity in ultrathin films in 1960(1). So far, research on interface superconductivity has focused on materials that are known to be superconductors in bulk. Here, we show that electrostatic carrier doping can induce superconductivity in KTaO(3), a material in which superconductivity has not been observed before. Taking advantage of the large capacitance of the self-organized electric double layer that forms at the interface between an ionic liquid and KTaO(3) (ref. 12), we achieve a charge carrier density that is an order of magnitude larger than the density that can be achieved with conventional chemical doping. Superconductivity emerges in KTaO(3) at 50 mK for two-dimensional carrier densities in the range 2.3 × 10(14) to 3.7 × 10(14) cm(-2). The present result clearly shows that electrostatic carrier doping can lead to new states of matter at nanoscale interfaces.
自 1960 年首次在超薄薄膜中证明电场可调超导性以来，人们一直在研究界面超导性（1）。到目前为止，界面超导性的研究主要集中在那些在体相中被认为是超导的材料上。在这里，我们表明静电载流子掺杂可以在 KTaO3 中诱导出超导性，而 KTaO3 以前没有观察到过超导性。利用在离子液体和 KTaO3 之间形成的自组织电双层的大电容（12），我们实现了比传统化学掺杂所能达到的载流子密度大一个数量级的载流子密度。在二维载流子密度为 2.3×10(14) 到 3.7×10(14)cm(-2)的范围内，KTaO3 在 50mK 时出现超导性。目前的结果清楚地表明，静电载流子掺杂可以在纳米尺度界面处导致新的物质状态。
