Anomalous Low-Temperature Enhancement of Supercurrent in Topological-Insulator Nanoribbon Josephson Junctions: Evidence for Low-Energy Andreev Bound States

Morteza Kayyalha, Mehdi Kargarian, Aleksandr Kazakov, Ireneusz Miotkowski, Victor M. Galitski, Victor M. Yakovenko, Leonid P. Rokhinson, Yong P. Chen

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30 Scopus citations

Abstract

We report anomalous enhancement of the critical current at low temperatures in gate-tunable Josephson junctions made from topological insulator BiSbTeSe2 nanoribbons with superconducting Nb electrodes. In contrast to conventional junctions, as a function of the decreasing temperature T, the increasing critical current Ic exhibits a sharp upturn at a temperature T∗ around 20% of the junction critical temperature for several different samples and various gate voltages. The Ic vs T demonstrates a short junction behavior for T>T∗, but crosses over to a long junction behavior for T<T∗ with an exponential T dependence Ic-exp(-kBT/δ), where kB is the Boltzmann constant. The extracted characteristic energy scale δ is found to be an order of magnitude smaller than the induced superconducting gap of the junction. We attribute the long-junction behavior with such a small δ to low-energy Andreev bound states arising from winding of the electronic wave function around the circumference of the topological insulator nanoribbon.

Original languageEnglish (US)
Article number047003
JournalPhysical review letters
Volume122
Issue number4
DOIs
StatePublished - 2019

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy

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