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Onset of a superconductor-insulator transition in an ultrathin NbN film under in-plane magnetic field studied by terahertz spectroscopy

M. Šindler, F. Kadlec, C. Kadlec

DOI 10.1103/PhysRevB.105.014506 · Physical Review B

T1

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Abstract

Optical conductivity of a moderately disordered superconducting NbN film was investigated by terahertz time-domain spectroscopy in an external magnetic field applied along the film plane. The film thickness of ∼5 nm was comparable with the coherence length, so vortices should not form. This was confirmed by the fact that no marked difference between the spectra with a terahertz electric field set perpendicular and parallel to the external magnetic field was observed. Simultaneous use of Maxwell-Garnett effective medium theory and the model of optical conductivity by Herman and Hlubina [Phys. Rev. B 96, 014509 (2017)] proved to correctly reproduce the terahertz spectra obtained experimentally in a magnetic field of up to 7 T. This let us conclude that the magnetic field tends to suppress the superconductivity, resulting in an inhomogeneous state where superconducting domains are enclosed within a normal-state matrix. The scattering rate due to pair-breaking effects was found to linearly increase with the magnetic field.

Source-reported materials — not catalogue approval

FormulaReported Tc (K)Pressure (GPa)Type
NbN

Archive — visibility unverified

Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.

13.9Pressure not reportedunknown
NbN

Archive — visibility unverified

Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.

15.2Pressure not reportedunknown
NbN

Archive — visibility unverified

Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.

15.5Pressure not reportedunknown
NbN

Archive — visibility unverified

Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.

12.8Pressure not reportedunknown

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