鐵硒碲與金的C軸方向穿隧元件中電導能譜與超導能隙結構之研究

我們將雷射濺鍍法成長出來的鐵硒碲薄膜製作成C方向的鐵硒碲-金穿遂元件，並研究分析該元件的電導能譜。實驗中，當量測的溫度低於鐵硒碲的超導溫度時，除了明顯的ZBCP現象產生外其它的類似超導能隙的結構也隨著鐵硒碲的超導特性而產生。由於這些結構隨著磁性以及溫度的變化，有著相應的反應，該結構可以被認定為與超導特性有關連。透過extended BTK理論的計算，我們的實驗結果可以被模擬出來，鐵硒碲的兩個超導能隙大小在兩個樣品中分別為4、6meV以及7、10.5meV。雖然兩個樣品上看到的數值有差異，不過兩個超導能隙的比例均為1.5。在更高偏壓的區域，我們還發現了另一個大結構的類超導能隙結構。除此之外，我們還發現了通氧可讓鐵硒碲薄膜的超導特性變好的結果。

關鍵字

鐵基超導；超導-金屬元件；電導能譜；超導能隙

並列摘要

The electric transport properties of superconducting c-axis FeSe0.3Te0.7/Au (S/N) junctions, fabricated using pulsed laser deposition, have been investigated in the temperature range of 2 K to the superconducting transition temperature Tc, and in the presence of applied magnetic fields from 0 to 9 T. A large zero-bias conductance peak has always been observed in every conductance spectrum of the junctions. In addition, we have found several gap-like features. Using the extended BTK theory with the currently favored nodeless s±-wave symmetry, our conductance spectrum can be reproduced qualitatively with Δ1 = 4 meV, and Δ2 = 6 meV at 2 K in sample #1 and Δ1 = 7 meV, and Δ2 = 10.5 meV at 2 K in sample #2. Although there is an inconsistency of the gap values in FeSeTe, the relative ratio between two gaps are both 1.5, which is the same as the published ARPES data for FeSeTe samples of similar compositions. We note that the experimental conductance spectra are substantially below the one calculated in the high bias range. Furthermore, there are unaccounted conductance minima at approximately 15.4 meV (20 meV) in junction #1 (#2) whatever the cause for these conductance minima may also be the reason for the discrepancy. In addition, we have accidentally encountered an interesting Tc enhancement effect due to oxygen-annealing effect for the pulse-deposited FeSeTe thin films. The Tc of the as-grown thin film can be increased up to 3 K after an oxygen-annealing process.

並列關鍵字

iron based superconductors ； c-axis superconductor-normal junction ； tunneling spectra ； gap structures

參考文獻

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鐵硒碲與金的C軸方向穿隧元件中電導能譜與超導能隙結構之研究

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