Dirac lines and loop at the Fermi level in the time-reversal symmetry breaking superconductor LaNiGa2
Dirac lines and loop at the Fermi level in the time-reversal symmetry breaking superconductor LaNiGa2
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DOI：
10.1038/s42005-021-00771-5
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发表时间：
2022-01-13
影响因子：
5.5
通讯作者：
Taufour, Valentin
中科院分区：
文献类型：
--
作者：
Badger, Jackson R.;Quan, Yundi;Taufour, Valentin
与传统超导体相比，非传统超导体的库珀对的对称性较低。在大多数非传统超导体中，额外的对称性破缺与典型成分有关，如强关联费米液相、磁涨落或非中心对称结构中的强自旋轨道耦合。在这篇文章中，我们证明了超导体LaNiGa2的时间反转对称性破缺是由其先前未知的拓扑电子能带结构实现的，在费米能级上具有狄拉克线和狄拉克回路。在自旋-轨道耦合下，两个对称性相关的狄拉克点甚至保持简并。这些独特的拓扑特征使得非传统的超导带隙可以在没有其他典型成分的情况下打破时间反转对称性。我们的发现为识别基于非对称对称的新型非传统超导体提供了一条途径，并将使未来发现拓扑晶体超导体成为可能。拓扑超导系统有望展示一系列奇异的物理，这对于量子计算技术的应用特别有用。在这里，作者报道了LaNiGa2的合成，由于其非对称晶体结构，它既具有拓扑特征又具有超导特征。
Unconventional superconductors have Cooper pairs with lower symmetries than in conventional superconductors. In most unconventional superconductors, the additional symmetry breaking occurs in relation to typical ingredients such as strongly correlated Fermi liquid phases, magnetic fluctuations, or strong spin-orbit coupling in noncentrosymmetric structures. In this article, we show that the time-reversal symmetry breaking in the superconductor LaNiGa2 is enabled by its previously unknown topological electronic band structure, with Dirac lines and a Dirac loop at the Fermi level. Two symmetry related Dirac points even remain degenerate under spin-orbit coupling. These unique topological features enable an unconventional superconducting gap in which time-reversal symmetry can be broken in the absence of other typical ingredients. Our findings provide a route to identify a new type of unconventional superconductors based on nonsymmorphic symmetries and will enable future discoveries of topological crystalline superconductors.Topological superconducting systems are expected to exhibit a range of exotic physics which are particularly useful for application in quantum computing technologies. Here, the authors report the synthesis of LaNiGa2 which exhibits both topological and superconducting features originating from its nonsymmorphic crystal structure.