Resonant Oscillations of Josephson Current in Nb‐Bi₂Te_2.3Se_0.7‐Nb Junctions

Abstract

Josephson proximity junctions and devices employing topological insulators are promising candidates for realizing topological superconductivity and topologically protected quantum circuits. Here, the new type of oscillations of the critical Josephson current in the ballistic Nb-Bi 2 Te 2.3 Se 0.7 -Nb junctions subject to the magnetic fields is reported. The oscillations appear below ≈400 mK and have a very unusual sharp-peaked shape. Their ultra-short period ≈1 Oe, by orders of magnitude shorter than the expected periodicity due to fluxoid quantization in the device, corresponds to the extremely low energy scale ≈1 𝛍eV. It is established that the observed effect is due to the resonant transmission of Andreev quasiparticles via the peculiar energy levels forming near the S-TI interfaces.

Revealing Intrinsic Superconductivity of the Nb/BiSbTe2Se Interface

“…[ 7–10 ] Therefore, the interface between topological insulator and superconductor plays an extremely important role in studying topological superconductivity. [ 11–14 ] Since the superconducting order parameter is sensitive to microscale structures around electrodes and their fabrication process, it is crucial to evaluate both the transport properties of superconducting junctions and their local structure to establish topological superconductivity.…”

“…[7][8][9][10] Therefore, the interface between topological insulator and superconductor plays an extremely important role in studying topological superconductivity. [11][12][13][14] Since the superconducting Highresolution high angle annular dark field scanning trans mission electron microscopy (HAADFSTEM) image of the FeBSTS is shown in Figure 1a. The electron diffraction image corresponds to the rhombohedral crystal structure with lattice constants a = 4.2 Å and c = 29.7 Å, which is consistent with previous measurements of similar TIs.…”

Revealing intrinsic superconductivity of the Nb/BiSbTe$_2$Se interface

“…[7][8][9][10] Therefore, the interface between topological insulator and superconductor plays an extremely important role in studying topological superconductivity. [11][12][13] Since the superconducting order parameter is sensitive to microscale structures around electrodes and their fabrication process, it is crucial to evaluate both the transport properties of superconducting junctions and their local structure to establish topological superconductivity.…”

Limitations of the Current–Phase Relation Measurements by an Asymmetric dc-SQUID

“…One of the main characteristics of a Josephson junction (JJ) is an associated current–phase relation (CPR), which by definition is the supercurrent dependence on the phase difference of the superconducting wave functions of the leads. Currently the Josephson effect is observed for countless types of weak links, such as normal metals, − ferromagnetic barriers, , nanobridges, − and various quantum materials such as graphene, , Dirac and Weyl semimetals, − and topological insulators (TIs). − …”