Suppression of Andreev conductance in a topological insulator–superconductor nanostep junction |
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引用本文: | 郑翌洁,宋俊涛,李玉现.Suppression of Andreev conductance in a topological insulator–superconductor nanostep junction[J].中国物理 B,2016,25(3):37301-037301. |
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作者姓名: | 郑翌洁 宋俊涛 李玉现 |
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作者单位: | College of Physics & Information Engineering and Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024, China |
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基金项目: | Project supported by the National Natural Science Foundation of China (Grant Nos. 11204065 and 11474085) and the Natural Science Foundation of Hebei Province, China (Grant Nos. A2013205168 and A2014205005). |
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摘 要: | When two three-dimensional topological insulators(TIs) are brought close to each other with their surfaces aligned,the surfaces form a line junction. Similarly, three TI surfaces, not lying in a single plane, can form an atomic-scale nanostep junction. In this paper, Andreev reflection in a TI–TI–superconductor nanostep junction is investigated theoretically. Because of the existence of edge states along each line junction, the conductance for a nanostep junction is suppressed. When the incident energy(ε) of an electron is larger than the superconductor gap(?), the Andreev conductance in a step junction is less than unity while for a plane junction it is unity. The Andreev conductance is found to depend on the height of the step junction. The Andreev conductance exhibits oscillatory behavior as a function of the junction height with the amplitude of the oscillations remaining unchanged when ε = 0, but decreasing for ε = ?, which is different from the case of the plane junction. The height of the step is therefore an important parameter for Andreev reflection in nanostep junctions, and plays a role similar to that of the delta potential barrier in normal metal–superconductor plane junctions.
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收稿时间: | 2015-08-05 |
Suppression of Andreev conductance in a topological insulator-superconductor nanostep junction |
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Institution: | College of Physics & Information Engineering and Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024, China |
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Abstract: | When two three-dimensional topological insulators (TIs) are brought close to each other with their surfaces aligned, the surfaces form a line junction. Similarly, three TI surfaces, not lying in a single plane, can form an atomic-scale nanostep junction. In this paper, Andreev reflection in a TI-TI-superconductor nanostep junction is investigated theoretically. Because of the existence of edge states along each line junction, the conductance for a nanostep junction is suppressed. When the incident energy (ε) of an electron is larger than the superconductor gap (Δ), the Andreev conductance in a step junction is less than unity while for a plane junction it is unity. The Andreev conductance is found to depend on the height of the step junction. The Andreev conductance exhibits oscillatory behavior as a function of the junction height with the amplitude of the oscillations remaining unchanged when ε=0, but decreasing for ε=Δ, which is different from the case of the plane junction. The height of the step is therefore an important parameter for Andreev reflection in nanostep junctions, and plays a role similar to that of the delta potential barrier in normal metal-superconductor plane junctions. |
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Keywords: | topological insulator nanostep junction suppression of Andreev conductance |
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