Josephson current mediated by ballistic topological states in Bi2Te2.3Se0.7 single nanocrystals

Abstract

Superconducting proximity devices using low-dimensional semiconducting elements enable a ballistic regime in the proximity transport. The use of topological insulators in such devices is considered promising owing to the peculiar transport properties these materials offer, as well the hope of inducing topological superconductivity and Majorana phenomena via proximity effects. Here we demonstrate the fabrication and superconducting properties of proximity Josephson devices integrating nanocrystals single of Bi 2 Te 2.3 Se 0.7 with a thickness of a few unit cells. Single junctions display typical characteristics of planar Josephson devices; junctions integrating two nanocrystals behave as nanodimensional superconducting quantum interference devices. A peculiar temperature and magnetic field evolution of the Josephson current along with the observed excess current effect point towards the ballistic proximity regime of topological channels. This suggests the proposed devices are promising for testing topological superconducting phenomena in two-dimensions.

Superconducting Long-Range Proximity Effect through the Atomically Flat Interface of a Bi2Te3 Topological Insulator

“…[4][5][6][7][8][9][10][11] Another possibility is the extension of the desired properties into a given material from a "source" material by proximity. In this way, the superconductivity can be induced in normal metals [12][13][14][15][16][17][18][19] or even in semiconductors, [20][21][22][23] but also a magnetism 24 or an enhanced spin-orbit coupling. [25][26][27][28] In this respect, the interface between superconductors (S) and a topological insulator (TI) is expected to induce by proximity peculiar properties such as unconventional superconductivity.…”

Lateral Josephson Junctions as Sensors for Magnetic Microscopy at Nano-Scale

“…5(i) has another important advantage: it has a very low amount of superconducting material located close to the studied sample and thus, by its poor diamagnetic screening, it is potentially less invasive than a SQUID-on-tip sensor [44]. Into the opposite, a long LJJ could be advantageous in cases when an increased field sensitivity due to field focusing effect in LJJ [45] or a high spatial resolution in one direction are required [46].…”

“…The second factor to consider is the effect of field focusing that we took into account via constant geometric factor α in Appendix B. This assumption is reasonable in a first approximation [18,45]. In general however, the spatially inhomogeneous field of the tip leads to a more complex distribution of Meissner currents in LJJ and, as a consequence of the non-local current-field relation, to a non-trivial screening magnetic field focusing.…”

Resonant Oscillations of Josephson Current in Nb‐Bi2Te2.3Se0.7‐Nb Junctions

“…Along with the low thickness and high quality of the TI-single crystals, it enables the ballistic transport of the Cooper pairs dominated by the flow along the surface channels of Bi 2 Te 2.3 Se 0.7 . [23] As a result of the Ar-etching, the nano-crystals under the Nbelectrodes get damaged and are characterized by the short electron mean free path. [26] Only a few ballistic channels remain wellconnected via these damaged regions.…”