德国科隆大学Yoichi Ando团队研究了超导体邻近拓扑绝缘体纳米线中的长程交叉安德烈夫反射。2025年3月11日出版的《自然—物理学》杂志发表了这项成果。

交叉安德烈夫反射是一种非局域输运现象，其在遥远的位置之间产生并检测库珀对相关性。这也是库珀对分裂产生远程纠缠的基础。尽管交叉安德烈夫反射在与超导体接近耦合的半导体中得到了广泛的研究，但在拓扑绝缘体中观察它非常困难。

研究组报告了在邻近拓扑绝缘体纳米线中观察到的这种效应。他们在介观器件上进行了局域和非局域电导光谱，其中超导铌和金属触点连接到体绝缘纳米线。在该局域电导测量中，研究组检测到硬间隙和可以达到零偏压的安德烈夫束缚态的出现。在扫描化学势时，他们偶尔也会观察到负的非局域电导，这为交叉安德烈夫反射提供了证据。

即使在比铌或近肟化纳米线的预期超导相干长度长得多的长度尺度上，也能检测到这种信号。研究组认为，这种长期效应是由于邻近纳米线中无序的复杂作用造成的。

附：英文原文

Title: Long-range crossed Andreev reflection in a topological insulator nanowire proximitized by a superconductor

Author: Feng, Junya, Legg, Henry F., Bagchi, Mahasweta, Loss, Daniel, Klinovaja, Jelena, Ando, Yoichi

Issue&Volume: 2025-03-11

Abstract: Crossed Andreev reflection is a non-local transport phenomenon that creates and detects Cooper pair correlations between distant locations. It is also the basis of Cooper pair splitting to generate remote entanglement. Although crossed Andreev reflection has been extensively studied in semiconductors proximity-coupled to a superconductor, observing it in a topological insulator has been very difficult. Here we report the observation of this effect in a proximitized topological insulator nanowire. We perform local and non-local conductance spectroscopy on mesoscopic devices in which superconducting niobium and metallic contacts are connected to a bulk-insulating nanowire. In our local conductance measurements we detect a hard gap and the appearance of Andreev bound states that can reach zero bias. We also occasionally observe a negative non-local conductance when sweeping the chemical potential, providing evidence of crossed Andreev reflection. This signal is detected even over length scales much longer than the expected superconducting coherence length of either niobium or the proximitized nanowire. We suggest that this long-range effect is due to the intricate role of disorder in proximitized nanowires.

DOI: 10.1038/s41567-025-02806-y

Source: https://www.nature.com/articles/s41567-025-02806-y