电子掺杂磷族铬化合物LaOCrAs的超导电性
Possible Superconductivity in Electron-doped Chromium Pnictide LaOCrAs
摘要：
根据第一性原理计算，我们构建了LaOCrAs的五个Cr $3d$轨道的紧束缚模型.在此基础上，我们利用泛函重整化群（FRG）研究了掺杂LaOCrAs中关联诱导的超导电性。我们发现，在电子掺杂的LaOCrAs中存在两个超导电性圆顶。随着电子掺杂的增加，系统的基态从母体化合物中的G-型反铁磁性演变成由源自$d_{3z^2-r^2}$轨道的电子带主导的初始$s_\pm$波超导相，因为填充物高于Cr的$d$轨道上的每个位置的$4.2$电子。能隙函数在带中心附近的费米口袋处具有较强的八重态各向异性，而在其他口袋处逐渐减小。在电子过掺杂的LaOCrAs中，系统出现了$d_{x^2-y^2}$波超导相，激活带来自于$d_{xy}$轨道。在两个超导圆顶之间，可能出现时间反演对称性破缺的$s+id$ SC相。在空穴掺杂的情况下，我们还发现了$s_\pm$波超导相。
英文摘要：
We constructed an effective tight-binding model with five Cr $3d$ orbitals for LaOCrAs according to first-principles calculations. Basing on this model, we investigated possible superconductivity induced by correlations in doped LaOCrAs using the functional renormalization group (FRG). We find that there are two domes of superconductivity in electron-doped LaOCrAs. With increasing electron doping, the ground state of the system evolves from G-type antiferromagnetism in the parent compound to an incipient $s_\pm$-wave superconducting phase dominated by electron bands derived from the $d_{3z^2-r^2}$ orbital as the filling is above $4.2$ electrons per site on the $d$-orbitals of Cr. The gap function has strong octet anisotropy on the Fermi pocket around the zone center and diminishes on the other pockets. In electron over-doped LaOCrAs, the system develops $d_{x^2-y^2}$-wave superconducting phase and the active band derives from the $d_{xy}$ orbital. Inbetween the two superconducting domes, a time-reversal symmetry breaking $s+id$ SC phase is likely to occur. We also find $s_\pm$-wave superconducting phase in the hole-doped case.
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