Shimizu Katsuya, Ishikawa Hiroto, Takao Daigoroh, Yagi Takehiko, Amaya Kiichi
Department of Physical Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
Nature. 2002 Oct 10;419(6907):597-9. doi: 10.1038/nature01098.
Superconductivity at high temperatures is expected in elements with low atomic numbers, based in part on conventional BCS (Bardeen-Cooper-Schrieffer) theory. For example, it has been predicted that when hydrogen is compressed to its dense metallic phase (at pressures exceeding 400 GPa), it will become superconducting with a transition temperature above room temperature. Such pressures are difficult to produce in a laboratory setting, so the predictions are not easily confirmed. Under normal conditions lithium is the lightest metal of all the elements, and may become superconducting at lower pressures; a tentative observation of a superconducting transition in Li has been previously reported. Here we show that Li becomes superconducting at pressures greater than 30 GPa, with a pressure-dependent transition temperature (T(c)) of 20 K at 48 GPa. This is the highest observed T(c) of any element; it confirms the expectation that elements with low atomic numbers will have high transition temperatures, and suggests that metallic hydrogen will have a very high T(c). Our results confirm that the earlier tentative claim of superconductivity in Li was correct.
基于传统的BCS（巴丁-库珀-施里弗）理论，低原子序数元素有望实现高温超导。例如，据预测，当氢被压缩到其致密金属相（压力超过400吉帕）时，它将成为超导材料，转变温度高于室温。在实验室环境中很难产生这样的压力，因此这些预测不容易得到证实。在正常条件下，锂是所有元素中最轻的金属，可能在较低压力下成为超导体；此前已有关于锂中超导转变的初步观察报告。在此我们表明，锂在压力大于30吉帕时成为超导体，在48吉帕时其转变温度（T(c)）与压力相关，为20K。这是所观测到的任何元素中最高的T(c)；它证实了低原子序数元素将具有高转变温度的预期，并表明金属氢将具有非常高的T(c)。我们的结果证实了锂中早期关于超导性的初步论断是正确的。
