Enhancement of the upper critical field by nonmagnetic impurities in dirty two-gap superconductors
By A. Gurevich. 2002
586 citations recorded by the source corpus.
Quasiclassic Usadel equations for two-band superconductors in the dirty limit are derived with the account of both intraband and interband scattering by nonmagnetic impurities. From these equations, the Ginzburg-Landau equations, and the equations for the critical temperature ${T}_{c}$ and the upper critical field ${H}_{c2}$ are obtained. The equation for ${H}_{c2}$ determines both the temperature dependence of ${H}_{c2}(T)$ and the orientational dependence of ${H}_{c2}(\ensuremath{\theta})$ as a function of the angle $\ensuremath{\theta}$ between $\mathbf{H}$ and the c axis. It is shown that the shape of the ${H}_{c2}(T)$ curve essentially depends on the ratio of the intraband electron diffusivities ${D}_{1}$ and ${D}_{2},$ and can be very different from the one-gap dirty-limit theory. In particular, value ${H}_{c2}(0)$ can considerably exceed ${0.7T}_{c}{\mathrm{dH}}_{c2}{/dT}_{c},$ which can have important consequences for applications of ${\mathrm{MgB}}_{2}.$ Based on a general equation for ${H}_{c2}(T,\ensuremath{\theta}),$ a scaling relation, which enables one to get the angular dependence of ${H}_{c2}(\ensuremath{\theta})$ from the equation for ${H}_{c2}$ at $\mathbf{H}\ensuremath{\Vert}c,$ is proposed. The behavior of ${H}_{c2}(\ensuremath{\theta})$ and ${H}_{c1}(\ensuremath{\theta})$ can deviate markedly from the results of the anisotropic Ginzburg-Landau theory, and the ratio of the upper critical field ${H}_{c2}^{\ensuremath{\Vert}}{/H}_{c2}^{\ensuremath{\perp}}$ for $\mathbf{H}\ensuremath{\Vert}\mathrm{ab}$ and $\mathbf{H}\ensuremath{\perp}\mathrm{ab}$ can both increase and decrease with temperature, depending on the relation between ${D}_{1}$ and ${D}_{2}.$ Implications of the obtained results for ${\mathrm{MgB}}_{2}$ are discussed.
Subfields: Condensed Matter Physics, Electronic, Optical and Magnetic Materials
View Paper: https://www.semanticscholar.org/paper/7f512ff4ab5a824ab5d4ffbcbf6aba4ab9b3659e
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In Condensed Matter Physics
In Electronic, Optical and Magnetic Materials
Citations in the corpus
- Two-band superconductor magnesium diboride (2008, background): “Both the temperature dependences of Hc2 and anisotropy illustrate that the two-band nature of superconductivity has a large impact on the applicability of the anisotropic Ginzburg–Landau theory in describing the properties of MgB2 [129, 141, 142].”
- Iron-based superconductors at high magnetic fields (2011, background): “For two bands, the equation for Hc2 can be written in the following conventional form [77, 115]:”