Hybrid Superconducting Junctions of Bi$_{2}$Se$_{3}$ Topological Insulator Nanoribbons

Topological insulators are exotic materials with bulk band gap and metallic edge states which are protected on their own boundary topologically. Here, we report on the fabrication and measurement results of the superconducting proximity junctions of topological insulator nanoribbons of Bi$_{2}$Se$_{3}$. Single-crystalline Bi$_{2}$Se$_{3}$ nanoribbons are synthesized using the vapor-liquid-solid method, while the superconducting Al electrodes are formed on top of the nanowire. When a magnetic field ($H)$ is applied along the axial direction, the magneto-resistance data exhibit quasi-periodic oscillations with an average periodicity of $H^{\ast } \quad \sim $ 0.4 T, which is consistent with the Aharonov-Bohm oscillations. In the superconducting state, the supercurrent branch with a critical current of $I_{c} \quad \sim $ 90 nA is clearly observed in the current-voltage curve as a result of the superconducting proximity effect in Bi$_{2}$Se$_{3}$ nanoribbon. Quantized voltage steps of the Bi$_{2}$Se$_{3}$ nanoribbon Josephson junction under the microwave irradiation satisfy the ac Josephson relation.