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arXiv · 2407.02383

Long-range crossed Andreev reflection in topological insulator nanowires proximitized by a superconductor

Junya Feng·Henry F. Legg·Mahasweta Bagchi·Daniel Loss·Jelena Klinovaja·Yoichi Ando
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Abstract

Crossed Andreev reflection (CAR) is a nonlocal transport phenomenon that creates/detects Cooper-pair correlations between distant places. It is also the basis of Cooper-pair splitting to generate remote entanglement. Although CAR has been extensively studied in semiconductors proximity-coupled to a superconductor, it has been very difficult to observe it in a topological insulator (TI). Here we report the first observation of CAR in a proximitized TI nanowire (TINW). We performed local and nonlocal conductance spectroscopy on mesoscopic TINW devices in which superconducting (Nb) and metallic (Pt/Au) contacts are made on a bulk-insulating TINW. The local conductance detected a hard gap, accompanied by the appearance of Andreev bound states that can reach zero-bias, while a negative nonlocal conductance was occasionally observed upon sweeping the chemical potential, giving evidence for CAR. Surprisingly, the CAR signal was detected even over 1.5 $\mu$m, which implies that pair correlations extend over a length scale much longer than the expected superconducting coherence length of either Nb or the proximitised TINW. Such a long-range CAR effect is possibly due to an intricate role of disorder in proximitized nanowires. Also, our 0.9-$\mu$m device presented a decent Cooper-pair splitting efficiency of up to 0.5.

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Junya Feng, Henry F. Legg, Mahasweta Bagchi, Daniel Loss, Jelena Klinovaja, Yoichi Ando. 2024-07-02. Long-range crossed Andreev reflection in topological insulator nanowires proximitized by a superconductor. https://doi.org/10.1038/s41567-025-02806-y

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