Long-range crossed Andreev reflection in topological insulator nanowires proximitized by a superconductor
arXiv:2407.02383 · doi:10.1038/s41567-025-02806-y
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 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-m device presented a decent Cooper-pair splitting efficiency of up to 0.5.
Revised version, 41 pages total; 29 pages of main text with 6 figures, 12 pages of supplement with 7 figures. The raw data and codes are available at the online depository Zenodo with the identifier DOI:10.5281/zenodo.12611922
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