We calculate the tunneling density of states (DOS) of MgB2 for different tunneling directions, by directly solving the real-axis, two-band Eliashberg equations (EE). Then we show that the numeric inversion of the standard singleband EE, if applied to the DOS of the two-band superconductor MgB2, may lead to wrong estimates of the strength of certain phonon branches (e.g. the E2g) in the extracte...

We report resistivity and magnetization of single crystal MgB2, focusing on the broadening of superconducting (SC) transition in magnetic fields. In-plane and outof-plane resistivity indicate that the broadening of superconducting transition is independent of Lorentz force and that it is merely dependent on the magnetic field direction. In magnetization, diamagnetic signal begins to appear at a...

We have performed high-resolution photoemission spectroscopy on MgB2 and observed opening of a superconducting gap with a narrow coherent peak. We found that the superconducting gap is s like with the gap value ( Delta) of 4.5+/-0.3 meV at 15 K. The temperature dependence (15-40 K) of the gap value follows well the BCS form, suggesting that 2Delta/k(B)T(c) at T = 0 is about 3. No pseudogap beha...

We succeeded in the synthesis of high-Jc MgB2 bulks via high energy ball-milling of elemental Mg and B powder at ambient temperatures. Alternatively to longtime mechanical alloying technique, the mixed powder was ball-milled for only 1h and the completed reaction is achieved by subsequent annealing. The correlations among synthesis parameters, microstructures and superconducting properties in M...

Cryogenic scanning tunneling microscopy and magnetization measurements were used to study the superconducting properties of MgB2. The magnetization measurements show a sharp superconductor transition at Tc = 39K, in agreement with previous works. The tunneling spectra exhibit BCS gap structures, with gap parameters in the range of 5 to 7 meV, yielding a ratio of 2∆/kBTc ∼ 3− 4. This suggests th...

We report on syntheses and electron transport properties of polycrystalline samples of diborides (AB2) with different transition metals atoms (A=Zr,Nb,Ta). The temperature dependence of resistivity, ρ(T ), and ac susceptibility of these samples reveal superconducting transition of ZrB2 with Tc = 5.5 K, while NbB2 and TaB2 have been observed nonsuperconducting up to 0.37 K. Hc2 (T) is linear in ...

Thermally-activated flux flow (TAFF) resistivity above the irreversibility field Bi is reported for two different c-axis textured MgB2 superconducting films. Transport measurements at different perpendicular magnetic fields 0,B,9 T and temperatures from 5 to 40 K reveal TAFF Ohmic resistivity rsT ,Bd for B.Bi described by the Arrhenius law, r=r0 exps-U /Td with the quadratic field dependence of...

Energy band structures are calculated for the new superconductor MgB2 and the related compounds by using the LDA and an FLAPW method. It is found that the strong three dimensional network in low-lying π bands brings about two dimensional σ holes in MgB2, which should be responsible for the superconductivity. The de Haas-van Alphen frequencies and the cyclotron masses are obtained for the Fermi ...