Superconducting energy gap distribution in c-axis oriented MgB${}_2$ thin film from point contact study

Abstract

We have analyzed about 100 voltage-dependent differential resistance dV/dI(V) curves of metallic point contacts between c-axis oriented MgB${}_2$ thin film and Ag, which exhibit clear Andreev reflection features connected with the superconducting gap. About one half of the curves show the presence of a second larger gap. The histogram of the double-gap distribution reveals distinct maxima at 2.4 and 7 meV, while curves with a single-gap features result in more broad maximum at 3.5 meV. The double-gap distribution is in qualitative agreement with the distribution of gap values over the Fermi surface calculated by H. J. Choi et al. (cond-mat/0111183). The data unequivocally show the presence of two gaps ${\Delta }_S=2.45\pm 0.15$ meV and ${\Delta }_L=7.0\pm 0.45$ meV in MgB${}_2$ with gap ratio $2.85\pm 0.15$. Our observations prove further a widely discussed multi-gap scenario for MgB${}_2$, where two distinct gaps are seen in the clean limit, while a single averaged gap is present in the dirty one.

V1:4 pages incl. 4 figures, RevTex4. V2: version for JETP Letters, 4 pages incl 3 Figs., jetpl.cls

References in corpus (14)

• Superconductivity of metallic boron in MgB_2
• Beyond Eliashberg superconductivity in MgB2: anharmonicity, two-phonon scattering, and multiple gaps
• Superconductivity in Dense $Mg{B}_2$ Wires
• Evidence for two superconducting energy gaps in MgB2 by point-contact spectroscopy
• Thermodynamic and Transport Properties of Superconducting $M{g}^{10}{B}_2$
• Two Gap State Density in MgB${}_2$: A True Bulk Property or A Proximity Effect?
• Scanning Tunneling Spectroscopy in MgB2
• Tunneling spectroscopy in small grains of superconducting MgB2
• Energy Gap from Tunneling and Metallic Sharvin Contacts onto MgB2: Evidence for a Weakened Surface Layer
• Tunneling spectroscopy measurement of the superconductor gap parameter of MgB_2
• Spectroscopic Evidence for Anisotropic S-Wave Pairing Symmetry in MgB2
• Superconducting energy gap distribution of MgB${}_2$ investigated by point-contact spectroscopy
• Symmetry and Temperature dependence of the Order parameter in MgB2 from point contact measurements
• Superconducting gap parameters of MgB2 obtained on MgB2/Ag and MgB2/In junctions

Cited by in corpus (14)

• Direct evidence for two-band superconductivity in MgB_2 single crystals from directional point-contact spectroscopy in magnetic fields
• Al substitution in MgB2 crystals: influence on superconducting and structural properties
• Time-resolved dynamics of the superconducting two-gap state in MgB2 thin films
• Scanning Tunneling Spectroscopy in MgB 2
• Phonon structure in I-V characteristic of MgB${}_2$ point-contacts
• Search for E_2g phonon modes in MgB_2 single crystals by point-contact spectroscopy
• Point-contact study of ReFeAs(1-x)Fx (Re=La, Sm) superconducting films
• Undergraduate experiment in point-contact spectroscopy with a Nb/Au junction
• Excess current in point contacts on two-band superconductor MgB${}_2$ in magnetic field
• Superconducting gap structure and pinning in disordered MgB2 films
• Features of Excess Conductivity Behavior in a Magnetic Superconductor Dy${}_{0.6}$Y${}_{0.4}$Rh${}_{3.85}$Ru${}_{0.15}$B${}_4$
• Study of the electron-phonon interaction in metal diborides MeB_2 (Me=Zr, Nb, Ta, Mg) by point-contact spectroscopy
• Isotropic multi-gap superconductivity in BaFe1.9Pt0.1As2 from thermal transport and spectroscopic measurements
• Transition Spectra for a BCS Superconductor with Multiple Gaps: Model Calculations for MgB_2