化学计量比FeTe中不同自旋涨落通道产生的竞争性扩展s波与d波配对
Competing Extended-$s$- and $d$-Wave Pairing from Distinct Spin-Fluctuation Channels in Stoichiometric $\mathrm{FeTe}$
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中文总结 AI 辅助
该研究构建FeTe的五轨道紧束缚模型，发现其存在竞争性的扩展s波与d_{x²-y²}波配对，配对类型随掺杂和相互作用强度变化，为FeTe的光谱测量提供了理论能隙结构。
中文摘要 AI 辅助
近期在化学计量比FeTe中观测到超导电性，这引发了一个问题：当间隙Fe被去除后，这种四方11型硫族化合物中的配对是如何形成的。我们基于第一性原理计算构建了受实验约束的五轨道紧束缚模型，并在涨落交换近似下处理电子关联与配对问题。线性化Eliashberg方程给出了竞争性的扩展s波与d_{x²-y²}波自旋单重态配对不稳定性。在接近化学计量比填充时，展开的单Fe布里渊区中(π,0)和(0,π)附近的自旋涨落连接了Γ/M空穴口袋与X/Y电子口袋，有利于在空穴和电子费米面之间改变符号的扩展s波能隙。当发生电子掺杂时，空穴口袋的耗尽使主导散射转向(π,π)附近的X-Y通道，使d_{x²-y²}波态成为主导不稳定性，其节点线避开了大部分费米面。随着填充度和相互作用强度的变化，两种配对通道的相对强度会发生改变，因为主导自旋涨落通道发生了变化。在匹配的相互作用强度、温度和填充度下，在所考虑的整个范围内，FeTe中的扩展s波本征值均大于FeSe中的，而d_{x²-y²}波本征值通常也更大，尤其在电子掺杂条件下。这些结果为化学计量比FeTe的光谱测量提供了可对比的具体能隙结构。
英文摘要
The recent observation of superconductivity in stoichiometric $\mathrm{FeTe}$ raises the question of how pairing develops in this tetragonal 11-type chalcogenide once interstitial Fe is removed. We construct an experimentally constrained five-orbital tight-binding model from first-principles calculations and treat electronic correlations and pairing within the fluctuation-exchange approximation. The linearized Eliashberg equation yields competing extended-$s$- and $d_{x^2-y^2}$-wave spin-singlet pairing instabilities. Near stoichiometric filling, spin fluctuations near $(π,0)$ and $(0,π)$ in the unfolded one-Fe Brillouin zone connect the $Γ/M$ hole pockets with the $X/Y$ electron pockets and favor an extended-$s$ gap that changes sign between the hole and electron sheets. Upon electron doping, depletion of the hole pockets shifts the dominant scattering toward the $X$--$Y$ channel near $(π,π)$, making the $d_{x^2-y^2}$-wave state the leading instability, with nodal lines that avoid most of the Fermi surface. The relative strengths of the two pairing channels vary with filling and interaction strength as the dominant spin-fluctuation channel changes. Under matched interaction strength, temperature, and filling, the extended-$s$ eigenvalue is larger in $\mathrm{FeTe}$ than in $\mathrm{FeSe}$ throughout the range considered, while the $d_{x^2-y^2}$-wave eigenvalue is also generally larger, particularly under electron doping. These results give concrete gap structures against which spectroscopic measurements of stoichiometric $\mathrm{FeTe}$ can be compared.
