Typically, topological superconductivity is reachable via proximity effect by a direct deposition of superconductor (S) on top of a topological insulator (TI) surface. Here, the double critical current in the Josephson junctions based on the topological insulator is observed in the fabricated planar Superconducting Quantum Interference Devicea. By measuring critical currents as a function of temperature and magnetic field, it is shown that the second critical current stems from the intrinsic superconductivity of the S–TI interface, which is supported by the modified Resistively Shunted Junction model and Transmission Electron Microscopy studies. This complex structure of the interface should be taken into account when the technological process involves Ar‐plasma cleaning.
Exotic quantum transport phenomena established in Josephson
junctions
(JJs) are reflected by a nonsinusoidal current–phase relation
(CPR). The solidified approach to measuring the CPR is via an asymmetric
dc-SQUID with a reference JJ that has a high critical current. We
probed this method by measuring CPRs of hybrid JJs based on the 3D
topological insulator (TI) Bi2Te2Se with a nanobridge
acting as a reference JJ. We captured both highly skewed and sinusoidal
critical current oscillations within single devices which contradict
the uniqueness of the CPR. This implies that the widely used method
provides inaccurate CPR measurement and leads to misinterpretation.
It was shown that the accuracy of the CPR measurement is mediated
by the asymmetry in derivatives of the CPRs but not in critical currents,
as was previously thought. Finally, we provided considerations for
an accurate CPR measurement via the most commonly used reference JJs.
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