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 language | English (US) |
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Article number | 047003 |
Journal | Physical review letters |
Volume | 122 |
Issue number | 4 |
DOIs | |
State | Published - 2019 |
All Science Journal Classification (ASJC) codes
- General Physics and Astronomy