Planar hybrid superconductor-normal metal-superconductor thin film junctions based on BaFe1.8Co0.2As2

Döring, Sebastian; Schmidt, S.; Schmidl, F.; Tympel, Volker; Haindl, S.; Kurth, F.; Iida, K.; Mönch, Ingolf; Holzäpfel, B.; Seidel, P.

doi:10.1016/j.physc.2012.03.030

Cited by 17 publications

(14 citation statements)

References 23 publications

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“…After the correction procedure we have usually observed a zerobias 1/ V -like singularity of the dc differential conductance for voltages smaller than the lower superconducting It should be stressed that it is not the first observation of steep zero-bias peaks with (0) 2 N G G > in point contacts of a normal counter-electrode with a superconductor. In particular, they have been observed for iron pnictide single crystals [24] and thin layers [25] as well as in Fe(Se, Te) films [26]. It can be that our interpretation of the anomalous zero-bias peaks is valid in these cases as well.…”

Section: Discussionsupporting

confidence: 58%

Tracing the evolution of the two energy gaps in magnesium diboride under pressure

Кононенко

Tarenkov

Belogolovskii

et al. 2015

Low Temperature Physics

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We have studied transport characteristics of mesoscopic multiple-mode superconducting contacts formed between two grains in bulk two-gap magnesium diboride. The experimental setup was realized by driving a normal-metal tip into MgB 2 polycrystalline sample and proved to be extremely stable, providing possibility to perform pressure experiments at low temperatures. It is argued that in our procedure a small piece of the superconducting electrode is captured by the tip apex and, as a result, two junctions in series are formed: a junction between a tip and MgB 2 grain and a mesoscopic disordered contact between two superconducting pellets. Although the relative weight of the first junction resistance was considerably less, its contribution is shown to be important for the comparison of measured data with expected gap values. Two hallmarks of multiple Andreev reflections inside the MgB 2 -c-MgB 2 contact (c stands for a high-transparent constriction), a zero-bias 1 / V -like singularity of the dc differential conductance and peaks connected to the two gap values, have been revealed. Finally, we report results of a hydrostatic compression experiment showing the evolution of the MgB 2 gap values with pressure. In contrast to the theoretical expectations, we have observed an increase of the smaller gap ∆ π whereas the larger gap ∆ σ decreased with increasing pressure as it should be for the electron-phonon pairing mechanism. We argue that the so-called separable model of anisotropy effects is insufficient to describe such changes and only improved two-band versions are capable to reproduce the pressure effect on the energy gaps in magnesium diboride.

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Section: Discussionsupporting

confidence: 58%

Tracing the evolution of the two energy gaps in magnesium diboride under pressure

Кононенко

Tarenkov

Belogolovskii

et al. 2015

Low Temperature Physics

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“…For a thickness of 5 nm of gold Josephson effect could be observed . At a gold barrier thickness of 10 nm it is not, but these junctions are more suitable for Andreev spectroscopy . The I–V characteristic shown in Fig.…”

Section: Electrical Characterisation Of the Junctionsmentioning

confidence: 99%

Josephson effects at iron pnictide superconductors: Approaching phase‐sensitive experiments

Schmidt

Döring

Hasan

et al. 2016

Physica Status Solidi (b)

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The electrical transport in the pnictides especially the quasiparticle tunnelling and Josephson effects in inhomogeneous superconducting systems can provide information on the symmetry of the order parameter. Different kinds of Josephson junctions with one or two pnictide electrodes were realised and their properties were experimentally studied in detail (e.g., current–voltage characteristics, microwave response, current‐phase relations, dependencies on temperature and external magnetic field). These results were compared to well‐known Josephson junctions and recent theories taking into account the special properties (multiband superconductivity, exotic pairing symmetry) of the pnictides. By combination of two junctions in different crystal directions with different barrier transparencies one forms corner junctions or SQUIDs as phase‐sensitive devices. If the technological problems can be solved the investigations on such devices will finally clear up the symmetry of the pnictides, directly. These investigations will lead to a better understanding of fundamental properties of the pnictides as well as to a realistic judgement on the potential for applications of pnictides in superconducting electronics and sensor applications, both established ones and novel ones utilising the special pnictide properties.

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“…28 Then we follow the processing steps from Ref. 27, covering the whole thin film with a 10 nm gold layer, pattering of base electrode via IBE, and forming the junction area by IBE and sputtering SiO 2 frameworks. Now we use a separate photo-lithographic mask, which covers the whole sample except an area including each junction window plus some tolerance area around.…”

Section: Junctions With Pnictide Electrodementioning

confidence: 99%

Investigation of TiOx barriers for their use in hybrid Josephson and tunneling junctions based on pnictide thin films

Döring

Monecke

Schmidt

et al. 2014

Journal of Applied Physics

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We tested oxidized titanium layers as barriers for hybrid Josephson junctions with high I c R n -products and for the preparation of junctions for tunneling spectroscopy. For that we firstly prepared junctions with conventional superconductor electrodes lead and niobium, respectively. By tuning the barrier thickness we were able to change the junctions' behavior from a Josephson junction to tunnel-like behavior applicable for quasi-particle spectroscopy. Subsequently, we transferred the technology to junctions using Co-doped BaFe 2 As 2 thin films prepared by pulsed laser deposition as base electrode and evaporated Pb as counter electrode. For barriers with a thickness of 1.5 nm we observe clear Josephson effects with I c R n ≈ 90 µV at 4.2 K. These junctions behave SNS'-like and are dominated by Andreev reflection transport mechanism. For junctions with barrier thickness of 2.0 nm and higher no Josephson but SIS'-or SINS'-like behavior with a tunnel-like conductance spectrum was observed.

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Planar hybrid superconductor-normal metal-superconductor thin film junctions based on BaFe1.8Co0.2As2

Cited by 17 publications

References 23 publications

Tracing the evolution of the two energy gaps in magnesium diboride under pressure

Tracing the evolution of the two energy gaps in magnesium diboride under pressure

Josephson effects at iron pnictide superconductors: Approaching phase‐sensitive experiments

Investigation of TiOx barriers for their use in hybrid Josephson and tunneling junctions based on pnictide thin films

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