We report an in-depth investigation on the out-of-plane lower critical field H _c1 of the KCa₂(Fe_1−x Co _x )₄As₄F₂ (12442-type, x = 0, 0.1). The multi-gap feature is revealed by the kink in the temperature-dependent H _c1(T) curve for the two samples with different doping levels. Based on a simplified two-gap model, the magnitudes of the two gaps are determined to be Δ ₁ = 1.2 meV and Δ ₂ = 5.0 meV for the sample with x = 0, Δ ₁ = 0.86 meV and Δ ₂ = 2.8 meV for that with x = 0.1. With the cobalt doping, the ratio of energy gap to critical transition temperature (Δ/k _B T _c) remains almost unchanged for the smaller gap and is suppressed by 20% for the larger gap. For the undoped KCa₂Fe₄As₄F₂, the obtained gap sizes are generally consistent with the results of angle-resolved photoemission spectroscopy experiments.

我们报告了对 KCa ₂ (Fe _{1− x} Co _x ) ₄ As ₄ F ₂ (12442 型, x = 0, 0.1)的面外下临界场H _{c1的深入研究。}具有不同掺杂水平的两个样品的温度相关H _c1 ( T ) 曲线中的扭结揭示了多间隙特征。基于简化的两间隙模型，对于_x = ₀、Δ 对于_{x =} 0.1，1 = 0.86 meV 和Δ ₂ = 2.8 meV 。在钴掺杂的情况下，能隙与临界转变温度的比值（Δ / k _B T _c）对于较小的间隙几乎保持不变，而对于较大的间隙则被抑制了 20%。对于未掺杂的KCa ₂ Fe ₄ As ₄ F ₂，得到的间隙尺寸与角分辨光电子能谱实验的结果基本一致。