title: Two-gap state density in MgB(2): a true bulk property or a proximity effect?
abstract: We report on the temperature dependence of the quasiparticle density of states in the simple binary compound MgB(2) directly measured using scanning tunneling microscope (STM). To achieve high quality tunneling conditions, a small crystal of MgB(2) is used as a tip in the STM experiment. The "sample" is chosen to be a 2H- NbSe(2) single crystal presenting an atomically flat surface. At low temperature the tunneling conductance spectra show a gap at the Fermi energy followed by two well-pronounced conductance peaks on each side. They appear at voltages V(S) approximately +/-3.8 mV and V(L) approximately +/-7.8 mV. With rising temperature both peaks disappear at the T(C) of the bulk MgB(2), a behavior consistent with the model of two-gap superconductivity. The possibility of a particular proximity effect is also discussed.
authors.affiliation: Physics Department and INFM Unit, University of Salerno, via S. Allende, 84081 Baronissi (SA), Italy.
authors.forename: F
authors.initials: F
authors.lastname: Giubileo
authors.forename: D
authors.initials: D
authors.lastname: Roditchev
authors.forename: W
authors.initials: W
authors.lastname: Sacks
authors.forename: R
authors.initials: R
authors.lastname: Lamy
authors.forename: D X
authors.initials: DX
authors.lastname: Thanh
authors.forename: J
authors.initials: J
authors.lastname: Klein
authors.forename: S
authors.initials: S
authors.lastname: Miraglia
authors.forename: D
authors.initials: D
authors.lastname: Fruchart
authors.forename: J
authors.initials: J
authors.lastname: Marcus
authors.forename: P
authors.initials: P
authors.lastname: Monod