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Above-gap differential conductance dips in superconducting point contacts

Applied Nanoscience volume 12, pages 761–768 (2022)Cite this article

Abstract

Point-contact Andreev spectroscopy is one of the most powerful techniques for obtaining quantitative energy and momentum-resolved information on the electronic properties of a superconductor. However, appropriate measurements often reveal unexpected conductance features that cannot be adequately modeled using conventional theory. In particular, these include conductance dips at voltage biases slightly exceeding the expected energy gap value for a superconductor. Guided by recent point-contact measurements of proximity-induced superconductivity in topological materials, we explain these features by inhomogeneous superconducting state in the studied material, conditionally divided into two parts with different gap values and a semitransparent potential barrier between them. To test this assumption, we designed a model experiment that mimics the main features of the model. The heterostructure under study is formed by an almost ideal point contact, formed using a new technology of self-textured nanofilaments based on the resistive-switching effect in a TiO2 film, a Pt counter-electrode, and a proximized Al/Ni0.5Cu0.5/NbN system, where superconducting correlations from the NbN superconductor are penetrating into a weak ferromagnetic Ni0.5Cu0.5 alloy in contact with an Al film. For a quantitative description of the conductance dips observed in all such devices and their evolution with temperature, we propose an extension of the conventional theory, the main element of which is a non-equilibrium-driven superconducting-to-normal transition and a crossover from coherent to sequential transmission in the Al/NiCu bilayer. Understanding the origin of the conductance dips imposes some restrictions on the explanation of induced superconductivity and paves the way for discovering novel superconducting materials with advanced properties.

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References

  • Aichner B, Jausner F, Zechner G, Mühlgassner R, Lang W, Klimov A, Puźniak R, Słysz W, Guziewicz M, Kruszka R, Węgrzecki M, Sobolewski R (2017) Superconducting order parameter fluctuations in NbN/NiCu and NbTiN/NiCu bilayer nanostripes for photon detection. Proc SPIE 10229:102290–102299

    Google Scholar 

  • Baltz V, Naylor AD, Seemann KM, Elder W, Sheen S, Westerholt K, Zabel H, Burnell G, Marrows CH, Hickey BJ (2009) Conductance features in point contact Andreev reflection spectra. J Phys Condens Matter 21:095701–1-095701–8

    Article  Google Scholar 

  • Belogolovskii M (2003) Phase-breaking effects in superconducting heterostructures. Phys Rev B 67:100503–1-100503–4

    Article  Google Scholar 

  • Belogolovskii M (2014) Charge tunneling across strongly inhomogeneous potential barriers in metallic heterostructures: a simplified theoretical analysis and possible experimental tests. Appl Surf Sci 312:17–22

    Article  CAS  Google Scholar 

  • Belogolovskii M, Zhitlukhina E, Lacquaniti V, De Leo N, Fretto M, Sosso A (2017) Intrinsically shunted Josephson junctions for electronics applications. Low Temp Phys 43:756–765

    Article  CAS  Google Scholar 

  • Blonder GE, Tinkham M, Klapwijk TM (1982) Transition from metallic to tunneling regimes in superconducting microconstrictions: excess current, charge imbalance, and supercurrent conversion. Phys Rev B 25:4515–4532

    Article  CAS  Google Scholar 

  • Büttiker M (1988) Coherent and sequential tunneling in series barriers. IBM J Res Dev 32:63–75

    Article  Google Scholar 

  • Daghero D, Gonnelli RS (2010) Probing multiband superconductivity by point-contact spectroscopy. Supercomd Sci Technol 23:043001–1-043001–37

    Google Scholar 

  • Dvoranová M, Plecenik T, Moško M, Vidiš M, Gregor M, Roch T, Grančič B, Satrapinskyy L, Kúš P, Plecenik A (2018) Point contact spectroscopy of superconductors via nanometer scale point contacts formed by resistive switching. AIP Adv 8:125217–1-125217–18

    Article  Google Scholar 

  • Herman F, Hlubina R (2016) Microscopic interpretation of the Dynes formula for the tunneling density of states. Phys Rev B 94:144508–1-144508–8

    Article  Google Scholar 

  • Hou X, Wang Z, Gu Y, He J, Chen D, Zhu W, Zhang M, Zhang F, Xu Y, Zhang S, Yang H, Ren Z, Weng H, Hao N, Lv W, Hu J, Chen G, Shan L (2019) Superconductivity induced at a point contact on the topological semimetal tungsten carbide. Phys Rev B 100:235109–1-235109–6

    Google Scholar 

  • Kashiwaya S, Tanaka Y, Koyanagi M, Kajimura K (1996) Theory for tunneling spectroscopy of anisotropic superconductors. Phys Rev B 53:2667–2676

    Article  CAS  Google Scholar 

  • Li F, Peng W, Wang Z (2019) The 0–π phase transition in epitaxial NbN/Ni60Cu40/NbN Josephson junctions. Chin Phys Lett 36:0474011–0474014

    Google Scholar 

  • Naidyuk YuG, Yanson IK (2005) Point-contact spectroscopy. Springer, New York, p 297

    Book  Google Scholar 

  • Naidyuk YuG, Kvitnitskaya OE, Efremov DV, Drechsler S-L (2020) Enhanced critical temperatures in the strongly overdoped iron-based superconductors AFe2As (A = K, Cs, Rb) observed by point contacts. Low Temp Phys 46:1070–1073

    Article  CAS  Google Scholar 

  • Nevirkovets IP, Belogolovskii MA, Ketterson JB (2020) Josephson junctions with artificial superparamagnetic barrier: a promising avenue for nanoscale magnetometry. Phys Rev Appl 14:014092–1-014092–7

    Article  Google Scholar 

  • Nikolić B, Allen PB (1999) Electron transport through a circular constriction. Phys Rev B 60:3963–3969

    Article  Google Scholar 

  • Parker WH (1995) Modified heating theory of nonequilibrium superconductors. Phys Rev B 12:3667–3672

    Article  Google Scholar 

  • Pepe GP, Latempa R, Parlato L, RuotoloA AG, Peluso G, Barone A, Golubov AA, YaV F, Kuptiyanov MYu (2006) Proximity effect in planar superconducting tunnel junctions containing Nb/NiCu superconductor/ferromagnet bilayers. Phys Rev B 73:054506–1-054506–8

    Article  Google Scholar 

  • Sheet G, Mukhopadhyay S (2004) Raychaudhuri P (2004) Role of critical current on the point-contact Andreev reflection spectra between a normal metal and a superconductor. Phys Rev B 69:1345071–1345076

    Article  Google Scholar 

  • Strijkers GJ, Ji Y, Yang FY, Chien CL, Byers JM (2001) Andreev reflections at metal/superconductor point contacts: measurement and analysis. Phys Rev B 63:104510–1-104510–6

    Article  Google Scholar 

  • Volkov S, Gregor M, Roch T, Satrapinskyy L, Grančič B, Fiantok F, Plecenik A (2019) Superconducting properties of very high quality NbN thin films grown by pulsed laser deposition. J Electr Eng 70:89–94

    Google Scholar 

  • Wiedenmann J, Liebhaber E, Kübert J, Bocquillon E, Burset P, Ames C, Buhmann H, Klapwijk TM, Molenkamp LW (2017) Transport spectroscopy of induced superconductivity in the three-dimensional topological insulator HgTe. Phys Rev B 96:165302–1-165302–8

    Article  Google Scholar 

  • Wolf EL (2012) Principles of Electron Tunneling Spectroscopy, 2nd edn. Oxford University Press, New York (ch. 5)

    Google Scholar 

  • Zhitlukhina E, Devyatov I, Egorov O, Belogolovskii M, Seidel P (2016) Anomalous inner-gap structure in transport characteristics of superconducting junctions with degraded interfaces. Nanoscale Res Lett 11:581–589

    Article  Google Scholar 

  • Zhitlukhina E, Belogolovskii M, Seidel P (2018) Engineering and tunable propagation of wave packets in superconducting quantum networks. IEEE Trans Appl Supercond 28:17002051–17002055

    Article  Google Scholar 

  • Zhitlukhina E, Dvoranová M, Plecenik T, Gregor M, Belogolovskii M, Plecenik A (2020) Electron-boson coupling in superconductors studied by a self-formed nanofilament device. Appl Nanosci 10:2617–2625

    Article  CAS  Google Scholar 

  • Zhu XJ, Shang J, Li RW (2012) Resistive switching effects in oxide sandwiched structures. Front Mater Sci 6:183–206

    Article  Google Scholar 

Download references

Funding

This work was supported by the Slovak Research and Development Agency under contracts no. APVV-19–303 and APVV-19–365 and by the Ministry of Education and Science of Ukraine (Project No. 0120U102059). It is also a result of the implementation of ITMS 26240220027 and 26210120010 projects supported by the Research & Development Operational Program funded by the ERDF.

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Authors and Affiliations

  1. Department of Experimental Physics, Faculty of Mathematics, Physics and Informatics, Comenius University in Bratislava, 84248, Bratislava, Slovak Republic

    Serhii Volkov, Maroš Gregor, Tomas Plecenik & Andrej Plecenik

  2. O.O. Galkin Donetsk Institute for Physics and Engineering, National Academy of Sciences of Ukraine, Kyiv, 03028, Ukraine

    Elena Zhitlukhina

  3. Vasyl’ Stus Donetsk National University, Vinnytsia, 21021, Ukraine

    Elena Zhitlukhina & Mikhail Belogolovskii

  4. G.V. Kurdyumov Institute for Metal Physics, National Academy of Sciences of Ukraine, Kyiv, 03142, Ukraine

    Mikhail Belogolovskii

Authors
  1. Serhii Volkov
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  2. Maroš Gregor
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  3. Tomas Plecenik
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  4. Elena Zhitlukhina
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  5. Mikhail Belogolovskii
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  6. Andrej Plecenik
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The authors contributed equally to the work.

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Correspondence to Mikhail Belogolovskii.

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Volkov, S., Gregor, M., Plecenik, T. et al. Above-gap differential conductance dips in superconducting point contacts. Appl Nanosci 12, 761–768 (2022). https://doi.org/10.1007/s13204-021-01734-6

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