title: Momentum-dependent multiple gaps in magnesium diboride probed by electron tunnelling spectroscopy.
abstract: The energy gap is the most fundamental property of a superconductor. MgB(2), a superconductor discovered in 2001, exhibits two different superconducting gaps caused by the different electron-phonon interactions in two weakly interacting bands. Theoretical calculations predict that the gap values should also vary across the Fermi surface sheets of MgB(2). However, until now, no such variation has been observed. It has been suggested that two gap values were sufficient to describe real MgB(2) samples. Here we present an electron tunnelling spectroscopy study on MgB(2)/native oxide/Pb tunnel junctions that clearly shows a distribution of gap values, confirming the importance of the anisotropic electron-phonon interaction. The gap values, and their spreads found from the tunnel junction measurements, provide valuable experimental tests for various theoretical approaches to the multi-band superconductivity in MgB(2).
authors.affiliation: Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA. kchen@temple.edu
authors.forename: Ke
authors.initials: K
authors.lastname: Chen
authors.forename: Wenqing
authors.initials: W
authors.lastname: Dai
authors.forename: C G
authors.initials: CG
authors.lastname: Zhuang
authors.forename: Qi
authors.initials: Q
authors.lastname: Li
authors.forename: Steve
authors.initials: S
authors.lastname: Carabello
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Lambert
authors.forename: Jerome T
authors.initials: JT
authors.lastname: Mlack
authors.forename: Roberto C
authors.initials: RC
authors.lastname: Ramos
authors.forename: X X
authors.initials: XX
authors.lastname: Xi
mesh_terms: D001896:Boron Compounds / Q000737:chemistry*; D004553:Electric Conductivity; D004566:Electrodes; D004583:Electrons; D007854:Lead; D017616:Magnesium Compounds / Q000737:chemistry*; D015233:Models, Statistical; D009038:Motion; D060739:Phonons; D056951:Photoelectron Spectroscopy / Q000379:methods*; D010825:Physics / Q000379:methods*; D012542:Scattering, Radiation; D013499:Surface Properties; D013696:Temperature
chemical_list: D001896:Boron Compounds; D017616:Magnesium Compounds; C078128:magnesium boride; D007854:Lead