μ + SR study of carbon-doped MgB 2 superconductors

μ + SR study of carbon - doped MgB 2 superconductors

2 00 1 Thermoelectric power and transport properties of pure and Al - doped MgB 2

We have measured the thermoelectric power, S, and resistivity, ρ, of pure and Al-doped MgB2. S is positive and increases linearly with temperature above the superconducting transition temperature, Tc. Deviations from the linear dependence appear at higher temperature, T > T0 ≈ 160K. Tc and T0 both decrease with Al doping whereas the slope of S(T) in the linear range increases with the Al conten...

The Gap Symmetry in Cuprate Superconductors and 2 MgB Due to Interband Pairing

In the Bardeen, Cooper, Schrieffer (BCS) theory of superconductivity, electron pairs are formed near the Fermi level comprised of ↑ k and ↓ − k electron pairs from the same band. We propose the existence of an additional type of Cooper pair consisting of ↑ k and ↓ − k electrons from different bands (Interband Cooper pairs). Interband Pairs (IBP) are only energetically possible in the vicinity o...

Direct Observation of Asymmetric Sr Diffusion in Sr--Doped La2CuO4

Superconductivity in copper oxides arises when a parent insulator compound is doped beyond some critical concentration [1]. In the case of La2CuO4 (LCO), high-Tc superconductivity is obtained either by substituting La 3+ with Sr 2+ or by inserting interstitial O 2[2]. Latest advance of the unique capabilities of layer-by-layer oxide molecular beam epitaxy (MBE) allows controlling the structural...

Transport Properties of Mgb 2

1. Introduction The discovery of the superconductivity in MgB 2 [1] at a temperature as high as 39 K has stimulated a enormous interest about the comprehension of its mechanism [2][3]. The study of the electron transport properties may give an insight into the normal state conduction process and into the electronic structure of MgB 2. From this point of view the results are contradictory. In fa...