Magnetic behavior of dirty multiband superconductors near the upper critical field

Abstract

Magnetic properties of dirty multiband superconductors near the upper critical field are studied. The parameter κ2 characterizing magnetization slope is shown to have a significant temperature variation which is quite sensitive to the pairing interactions and relative strengths of intraband impurity scattering. In contrast to single-band superconductors the increase of κ2 at low temperatures can be arbitrary large determined by the ratio of minimal and maximal diffusion coefficients in different bands. Temperature dependencies of κ2(T ) in two-band MgB2 and iron-based superconductors are shown to be much more sensitive to the multiband effects than the upper critical field Hc2(T ).PACS numbers:

Magnetization Signature of Topological Surface States in a Non‐Symmorphic Superconductor

“…For single-band superconductors, 𝜅 𝑇 is known to vary little (< 20%) with 𝑇 so that its value remains close to 𝜅 . In our case, 𝜅 /𝜅 changes by a factor of 2, which corresponds to a multi-band superconductor with Fermi surfaces having different symmetries, [34,35] in agreement with the electronic structure of In 2 Bi.…”

“…This combination of quasi‐2D and 3D Fermi surfaces has profound implications for superconductivity and, in particular, explains the unusual linear T dependence of H c2 and H c3 (Figure 2d). Such behavior is in fact expected for multiband superconductivity arising simultaneously from 2D‐ and 3D‐type Fermi surfaces [ 34,35 ] (for details, see ‘Temperature dependence of H c2 : fitting to the multiband theory’ in Supporting Information). The multiband superconductivity in In 2 Bi and the importance of the contribution from 2D In 1 Bi 1 sheets characterized by non‐symmorphic symmetry are also corroborated by Figure 4b that shows pronounced changes in the shape of magnetization curves with increasing T .…”

“…At low T, In 2 Bi exhibits 𝑀 𝐻 typical for conventional type-II superconductors with low , but the dependence becomes borderline type-I closer to 𝑇 (see the curve at 5.6 K). This can be quantified [35] using the ratio of the Ginzburg-Landau (GL) parameter 𝜅 and the Maki parameter 𝜅 obtained from the magnetization slope 𝑑𝑀 𝑑𝐻 ⁄ close to 𝐻 c2 :…”

Vortex motion and flux-flow resistivity in dirty multiband superconductors

“…For that one needs to know the Maki parameter also known as a generalized Ginzbirg-Landau parameter κ 2 which determines in particular the order parameter density as a function of magnetic field near H c2 11 . Recently this parameter has been calculated for multiband superconductors 24 . To obtain a complete picture of the flux-flow conductivity behaviour in multiband systems we consider also the regime of small magnetic fields, when a picture of isolated moving vortices is an adequate description 9 suggest the borderline regime when one of the superconducting bands is moderately clean and the other one is moderately dirty 29 .…”

Flux flow spin Hall effect in type-II superconductors with spin-splitting field

“…At low temperatures, the space- average spin current can be written in the intuitively transparent expressionwhere is the average spin density deviation from the normal state. The absolute magnitude of is determined by the average order parameter amplitude which can be found analytically using the expression for the order parameter amplitude near the upper critical field 56,57 . Then, substituting derived in the Supplementary Material and taking into account that the vortex velocity is we obtain the following analytical expression for the spin Hall angle , as a function of the average magnetic induction at low temperatures,where the Abrikosov parameter equals for the triangular and for the square lattice 58 .…”