Properties of niobium superconducting bridges prepared by electron-beam lithography and ion implantation

Gu, Jyongsil; Cha, Wongoon; Gamo, Kenji; Namba, Susumu

doi:10.1063/1.325736

Cited by 27 publications

(14 citation statements)

References 14 publications

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“…The junction area calculated from the junction geometry is 0.3 µm 2 , which is inconsistent with the area of 0.81 µm 2 evaluated from the distance between second and third nodes. Similar inconsistency has been previously assigned to the flux focusing effect 34,35 .…”

Section: Resultssupporting

confidence: 82%

Experimental study of ac Josephson effect in gate-tunable (Bi1−xSbx)2Te3 thin-film Josephson junctions

et al. 2020

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We report on measurements of the ac Josephson effect in three-dimensional topological insulator (TI) Josephson junctions with Fermi energy tuning using a back gate. We successfully tune the Fermi energy into the bulk gap of the TI. We observe that the Josephson energy as a function of the gate voltage has a dip feature, indicating the presence of specular Andreev reflections. We study the ac Josephson effect with detection of both Shapiro steps and Josephson emission. The obtained results show no signature of Majorana modes. With the support of simulations, we conclude that the observation of the fractional ac Josephson effect may be complicated by both a large parallel capacitance and a small ratio of current carried in 4π period modes compared to conventional 2π modes.

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Section: Resultssupporting

confidence: 82%

Experimental study of ac Josephson effect in gate-tunable (Bi1−xSbx)2Te3 thin-film Josephson junctions

et al. 2020

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“…The effective magnetic field present at the contact due to focusing of the applied field B 0 by Meissner screening currents in the electrodes was calculated by B eff ϭ(2W/d) 2/3 ϫB 0 . 17 The best fit was obtained by assuming a contact area of 70% of the area defined by lithography. This fit is shown by the dash-dotted curve in Fig.…”

mentioning

confidence: 99%

Local suppression of Josephson currents in niobium/two-dimensional electron gas/niobium structures by an injection current

et al. 1999

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We investigated niobium-AlGaSb/InAs-niobium hybrid structures using a high mobility two-dimensional electron gas as a weak link. The Josephson current observed in this structure was suppressed by an injection current driven into the weak link via an additional normal lead. Using a four-terminal configuration the supercurrent is suppressed all over the weak link. In a three-terminal configuration it was possible to suppress the supercurrent locally. ͓S0163-1829͑99͒06217-7͔The semiconductor/superconductor hybrid structure has been the subject of extensive research during the last years, to prove its suitableness as an interface between superconductor and semiconductor electronics. Especially the control of the supercurrent in a weak-link structure has attracted considerable interest in recent years. 1 One approach was to transfer the well-known semiconductor field effect transistor to superconductor/two-dimensional electron gas ͑2DEG͒ structures as proposed by Clark et al. 2 The supercurrrent flowing through the 2DEG was switched off by reducing the coherence length in the channel by applying a negative gate voltage. 3,4 Since the voltage necessary for depleting the electrons in the 2DEG channel is typically of the order of the band gap of the semiconductor and the output signal of the order of the superconducting gap of the electrodes, a voltage gain is hard to achieve. An alternative concept to avoid this problem is controlling the supercurrent by the injection of electrons via an additional nonsuperconductive contact into the weak link. [5][6][7][8] The energy of these carriers should be only of the order of the superconducting gap of the electrodes. Very recently, the control of the supercurrent by an injection current was experimentally succeeded for a Nb/Au weak link structure. 9 This system was in the diffusive regime with inelastic scattering processes thermalizing the injected carriers.In our current-controlled structure the superconductor Nb was contacted to a high-mobility two-dimensional electron gas ͑2DEG͒ in an Al 0.2 Ga 0.8 Sb/InAs heterostructure. Due to the high electron mobility the carrier transport from one Nb electrode to the opposite one can be considered to be ballistic. In addition inelastic scattering should become relevant only for higher temperatures. For weak links without inelastic scattering an even more efficient tuning of the Josephson current was predicted compared with the case of inelastic scattering present. 10 It will be shown that if a current is injected via Ohmic contacts into the 2DEG in a four-terminal configuration the supercurrent can be suppressed completely. In a three-terminal configuration it was possible to suppress the supercurrent locally, which was proven by measuring and fitting the interference patterns of the Josephson current appearing when a magnetic field is applied to the weak link.The heterostructure which forms the weak link in our structure was grown by molecular-beam epitaxy on a semiinsulating GaAs substrate. After a 1100 nm Al-Ga-Sb buffer layer, a 5...

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“…This value corresponds to the critical field B C . It is noted that because of flux-focusing by the diamagnetic Nb electrode, the magnetic field in the 2DEG is enhanced over the applied field by a factor of up to F = (2W/L) 2/3 [15]. The geometry of the junction used in the present study yielded F = 11.7 and this value of F gives a B C ≈ 82 Gauss.…”

Section: Conductance Enhancement Due To Coherent Andreev Reflectionmentioning

confidence: 89%

A superconductor/semiconductor/superconductor junction with a long-split gate

Takayanagi

Toyoda

Akazaki

1999

Superlattices and Microstructures

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Properties of niobium superconducting bridges prepared by electron-beam lithography and ion implantation

Cited by 27 publications

References 14 publications

Experimental study of ac Josephson effect in gate-tunable (Bi1−xSbx)2Te3 thin-film Josephson junctions

Experimental study of ac Josephson effect in gate-tunable (Bi1−xSbx)2Te3 thin-film Josephson junctions

Local suppression of Josephson currents in niobium/two-dimensional electron gas/niobium structures by an injection current

A superconductor/semiconductor/superconductor junction with a long-split gate

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