On Summation of Sequences

Anisotropic properties of MgB2 by torque magnetometry

“…We will show that there is good agreement in the form of the deviations of Hc2(θ) from AGLT between our torque results and the calculations of Ref. [5]. Calculations [6] also predicted an anisotropy of the penetration depth γ λ ≪ γH at low T .…”

“…However, the deviations found experimentally are most pronounced near Tc, while the calculations [3] predict pronounced deviations at low temperature T only. Recently, new calculations of Hc2(θ) were carried out for the (intra-band) dirty limit [4,5]. We will show that there is good agreement in the form of the deviations of Hc2(θ) from AGLT between our torque results and the calculations of Ref.…”

Ginzburg-Landau theory of vortices in a multigap superconductor

“…Such a temperature behavior has been recently addressed in a number of theoretical works based on various forms of the two-band BCS theory. 24,25,26,27 We suggest here a simpler description of the above effect within the two-gap Ginzburg-Landau theory.…”

“…withα 1,2 = α 1,2 + 13K 1,2 h. Subsequent calculations follow closely the single-gap case from the preceding subsection. The angular dependent part of the free energy is obtained by substituting (27) into the fourth-order terms:…”

“…13,14,15,16,17,18,19 Quantitative analysis of various thermodynamic and transport properties in the superconducting state of MgB 2 was made in the framework of the two-band BCS model. 20,21,22,23,24,25,26,27,28 An outside observer would notice, however, a certain lack of effective Ginzburg-Landau or London type theories applied to MgB 2 . This fact is explained of by quantitative essence of the discussed problems, though effective theories can often give a simpler insight.…”