论文标题
非中心对称超导体的拓扑属性
Topological properties of non-centrosymmetric superconductors $T$Ir$_{2}$B$_{2}$ ($T$=Nb, Ta)
论文作者
论文摘要
最近的一项实验报告了两个新的非中心对称超导体nbir $ _ {2} $ b $ _ {2} $和Tair $ _ {2} $ b $ _ {2} $，具有相应的超导过渡温度为7.2 k和5.2 k和5.2 k，并进一步提出了他们的超级尺度，以无效的态度。 górnicka\ textit {et al}。，adv。功能。母校。 2007960（2020）]。在这里，基于第一原理的计算和对称分析，我们建议$ t $ ir $ _ {2} $ b $ _ {2} $（$ t $ = nb，ta）是正常状态下的拓扑Weyl金属。在没有旋转轨道耦合（SOC）的情况下，我们发现NBIR $ _ {2} $ b $ _ {2} $具有12个Weyl点，而Tair $ _ {2} $ _ {2} $ b $ _ {2} $具有4个Weyl，即在时间逆转到逆转对称下的最小数字。同时，它们俩都有一个由三个淋巴结线组成的节点网。在存在SOC的情况下，镜面平面上的一个节点环与Weyl点一起演变成两个沙漏的Weyl环，这些环由非词形滑动镜像对称性决定。除了戒指外，nbir $ _ {2} $ b $ _ {2} $和Tair $ _ {2} $ b $ _ {2} $分别具有16对Weyl点。明确证明了表面费米弧。在Tair $ _ {2} $ b $ _ {2} $的（110）表面上，我们发现位于1.4 MEV的FERMI级别1.4 MEV的表面Fermi Arcs（$ \ sim $ 0.6 $ 0.6 $ 0.6 $ {\textÅ}^{ - 1} $）在实验中应轻松探究。因此，结合固有的超导性和非平凡的散装费米表面，$ t $ ir $ _ {2} $ b $ _ {2} $可能会提供一个非常有前途的平台，以探索三维拓扑超级传导性。
A recent experiment reported two new non-centrosymmetric superconductors NbIr$_{2}$B$_{2}$ and TaIr$_{2}$B$_{2}$ with respective superconducting transition temperatures of 7.2 K and 5.2 K and further suggested their superconductivity to be unconventional [K. Górnicka \textit{et al}., Adv. Funct. Mater. 2007960 (2020)]. Here, based on first-principles calculations and symmetry analysis, we propose that $T$Ir$_{2}$B$_{2}$ ($T$=Nb, Ta) are topological Weyl metals in the normal state. In the absence of spin-orbit coupling (SOC), we find that NbIr$_{2}$B$_{2}$ has 12 Weyl points, and TaIr$_{2}$B$_{2}$ has 4 Weyl points, i.e. the minimum number under time-reversal symmetry; meanwhile, both of them have a nodal net composed of three nodal lines. In the presence of SOC, a nodal loop on the mirror plane evolves into two hourglass Weyl rings, along with the Weyl points, which are dictated by the nonsymmorphic glide mirror symmetry. Besides the rings, NbIr$_{2}$B$_{2}$ and TaIr$_{2}$B$_{2}$ have 16 and 20 pairs of Weyl points, respectively. The surface Fermi arcs are explicitly demonstrated. On the (110) surface of TaIr$_{2}$B$_{2}$, we find extremely long surface Fermi arcs ($\sim$0.6 ${\textÅ}^{-1}$) located 1.4 meV below the Fermi level, which should be readily probed in experiment. Combined with the intrinsic superconductivity and the nontrivial bulk Fermi surfaces, $T$Ir$_{2}$B$_{2}$ may thus provide a very promising platform to explore the three-dimensional topological superconductivity.
