تقرير
Protected gap closing and reopening in topological-insulator Josephson junctions
| العنوان: | Protected gap closing and reopening in topological-insulator Josephson junctions |
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| المؤلفون: | Schluck, Jakob, Nikodem, Ella, Montag, Anton, Ziesen, Alexander, Bagchi, Mahasweta, Hassler, Fabian, Ando, Yoichi |
| سنة النشر: | 2024 |
| المجموعة: | Condensed Matter |
| مصطلحات موضوعية: | Condensed Matter - Superconductivity, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, Condensed Matter - Strongly Correlated Electrons |
| الوصف: | In the seminal proposal by Fu and Kane, the superconducting proximity effect was predicted to transform the surface state of a topological insulator (TI) into a topological superconductor, forming a nonchiral 1D Majorana state within a linear Josephson junction on the TI surface. The hallmark of this 1D Majorana state is a robust gap closing as a function of the superconducting phase difference $\varphi$ across the junction, which alternates in and out of the topological phase. These topological phase-transitions occur at $\varphi = (2n+1)\pi$ with integer $n$, leading to a $4\pi$-periodicity of the ground state. While the $4\pi$-periodicity has been indirectly inferred in the AC Josephson effect, the direct observation of the 1D Majorana state in a TI Josephson junction has remained contentious. Here, we report the direct observation of topological phase-transitions in a TI Josephson junction, where the local density of states is probed via tunnel contacts and $\varphi$ is controlled by a flux loop. The observed transitions are independent of the chemical potential, reinforcing their topological origin. Under an applied perpendicular magnetic field, Josephson vortices form, making $\varphi$ position-dependent. In this case, the gap closing occurs locally at the Josephson vortex cores where $\varphi = (2n+1)\pi$, which we also observe. Our findings provide direct confirmation of the Fu-Kane proposal and robust evidence for the emergence of topological superconductivity in a TI Josephson junction. Comment: 36 pages total; 26 pages of main text with 4 figures, 10 pages of supplement with 5 figures. The raw data and codes are available at the online depository Zenodo with the identifier 10.5281/zenodo.11615514 |
| نوع الوثيقة: | Working Paper |
| URL الوصول: | http://arxiv.org/abs/2406.08265 |
| رقم الأكسشن: | edsarx.2406.08265 |
| قاعدة البيانات: | arXiv |
| الوصف غير متاح. |