NaAlSi：一种含有自由电子和共价空穴的自掺杂半金属超导体
NaAlSi: a self-doped semimetallic superconductor with free electrons and covalent holes
摘要：
具有铁磷属元素化物“111”结构的三元层状sp导体NaAlSi在7 K下超导。使用密度泛函方法，我们表明，这种化合物是一种固有的（自掺杂）低载流子密度半金属与一些不寻常的功能。共价的Al-Si价带提供空穴，而在相邻Si层之间的沟道中传播的自由电子状Al 3s带刚好低于费米能级以产生电子载流子。费米能级（以及超导载流子）位于态密度的赝能隙内的一个狭窄而尖锐的峰。小峰来自于价带，这些价带几乎是纯Si的，准二维的，平坦的，并且与Al导带耦合。在1.6 K以上不超导的同构NaAlGe，除了少了一块小费米面外，几乎具有完全相同的能带结构。计算和讨论了Si和Na沿c轴位移引起的形变势。配对的机制似乎与其他几种轻掺杂的二维半导体（TiNCl，ZrNCl，HfNCl）有关，这还不是很清楚，但显然不是声子起源。
英文摘要：
The layered ternary sp conductor NaAlSi, possessing the iron-pnictide "111" crystal structure, superconducts at 7 K. Using density functional methods, we show that this compound is an intrinsic (self-doped) low-carrier-density semimetal with a number of unusual features. Covalent Al-Si valence bands provide the holes, and free-electron-like Al 3s bands, which propagate in the channel between the neighboring Si layers, dip just below the Fermi level to create the electron carriers. The Fermi level (and therefore the superconducting carriers) lies in a narrow and sharp peak within a pseudogap in the density of states. The small peak arises from valence bands which are nearly of pure Si, quasi-two-dimensional, flat, and coupled to Al conduction bands. Isostructural NaAlGe, which is not superconducting above 1.6 K, has almost exactly the same band structure except for one missing piece of small Fermi surface. Certain deformation potentials induced by Si and Na displacements along the c-axis are calculated and discussed. It seems likely that the mechanism of pairing is related to that of several other lightly doped two-dimensional nonmagnetic semiconductors (TiNCl, ZrNCl, HfNCl), which is not well understood but apparently not of phonon origin.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
