Energy Gap from Tunneling and Metallic Sharvin Contacts onto MgB2: Evidence for a Weakened Surface Layer

Abstract

Point-contact tunnel junctions using a Au tip on sintered MgB2 pellets reveal a sharp superconducting energy gap that is confirmed by subsequent metallic Sharvin contacts made on the same sample. The peak in the tunneling conductance and the Sharvin contact conductance follow the BCS form, but the gap values of 4.3 meV are less than the weak-coupling BCS value of 5.9 meV for the bulk Tc of 39 K. The low value of Delta compared to the BCS value for the bulk Tc is possibly due to chemical reactions at the surface.

3 pages, 3 figures

References in corpus (3)

• Strongly linked current flow in polycrystalline forms of the new superconductor MgB2
• Boron Isotope Effect in Superconducting MgB${}_2$
• Scanning Tunneling Spectroscopy in MgB2

Cited by in corpus (54)

• Beyond Eliashberg superconductivity in MgB2: anharmonicity, two-phonon scattering, and multiple gaps
• Specific Heat of Mg ^{11}B_2
• Two Gap State Density in MgB${}_2$: A True Bulk Property or A Proximity Effect?
• Two-Band Superconductivity in MgB2
• The reduced total isotope effect and its implications on the nature of superconductivity in MgB2
• Probing multiband superconductivity by point-contact spectroscopy
• Evidence for Two Superconducting Gaps in $Mg{B}_2$
• Phonon Density-of-States in MgB2
• Evidence for Two-Band Superconductivity from Break Junction Tunneling on MgB2
• Far-infrared optical conductivity gap in superconducting MgB2 films
• Strong Electron-Phonon Coupling in Superconducting MgB${}_2$: A Specific Heat Study
• Optical conductivity and penetration depth in MgB2
• Penetration Depth Measurements in MgB_2: Evidence for Unconventional Superconductivity
• Energy gap, penetration depth and surface resistance of MgB2 thin films determined by microwave resonator mesurements
• Spectroscopic Evidence for Anisotropic S-Wave Pairing Symmetry in MgB2
• Correlation between the residual resistance ratio and magnetoresistance in MgB2
• X-ray Photoemission Study of MgB2
• Reflection of two-gap nature in penetration depth measurements of MgB${}_2$ film
• Electron-Phonon or Hole Superconductivity in $Mg{B}_2$?
• The structure of the superconducting gap in MgB2 from point-contact spectroscopy
• Superconducting anisotropy and evidence for intrinsic pinning in single crystalline MgB${}_2$
• Break-Junction Tunneling on MgB_2
• Scanning Tunneling Spectroscopy in MgB 2
• Point-contact spectroscopy of MgB2
• Superconducting energy gap distribution of MgB${}_2$ investigated by point-contact spectroscopy
• Strong Coupling and Double Gap Density of States in Superconducting MgB2
• Superconducting properties and c-axis superstructure of Mg1-xAlxB2
• Electronic structure of MgB${}_2$: X-ray emission and absorption studies
• Far-infrared transmission studies of c-axis oriented superconducting MgB2 thin film
• Dependence of the flux creep activation energy on current density and magnetic field for MgB2 superconductor
• Field-induced quasiparticle excitations in novel type II superconductors
• Soft x-ray spectroscopy experiments on the near K-edge of B in MB2 (M=Mg, Al, Ta, and Nb)
• Quasiparticle Excitations outside the Vortex Cores in MgB${}_2$ Probed by Muon Spin Rotation
• A first-principles study of MgB2 (0001) surfaces
• Reversible magnetization of MgB2 single crystals with a two-gap nature
• A Directly Coupled Superconducting Quantum Interference Device Magnetometer Fabricated in Magnesium Diboride by Focused Ion Beam
• Surface and Image-Potential States on the MgB_2(0001) Surfaces
• Surface effects in multiband superconductors. Application to MgB${}_2$
• Superconducting energy gap distribution in c-axis oriented MgB${}_2$ thin film from point contact study
• Energy gap and proximity effect in $Mg{B}_2$ superconducting wires
• X-ray photoelectron spectroscopy studies of non-stoichiometric superconducting NbB2+x
• Superconducting energy gap in MgB2 film observed by infrared reflectance
• The degradation of MgB2 under ambient environment
• Reversible magnetization measurement of the anisotropy of the London penetration depth in MgB2 single crystals
• Temperature and Field Dependence of the Energy Gap of MgB2/Pb planar junction
• Magnetic monopoles in a charged two-condensate Bose-Einstein system
• Tunnel junctions on as-grown superconducting MgB2 thin films
• Temperature and junction-type dependency of Andreev reflection in MgB2
• Effects of Ion Milling on the Microwave Properties of MgB2 Films
• Strong charge transfer effects in the Mg2p^{-1} core-level spectrum of MgB_2
• Pseudogap and Conduction Dimensionalities in High-T_c Superconductors
• Optical Conductivity in a Two-Band Superconductor: Pb
• Is Delta_{pi}-gap-only superconductivity possible in Mg_{1-x}Al_{x}B_{2} and Mg(B_{1-y}C_{y})_{2} alloys?
• Superconducting energy gaps, low temperature specific heat, and quasiparticle spectra of MgB2