Multi-band $s_{++}$ superconductivity in ${\text{V}}_3\text{Si}$ determined from the response to a controlled disorder

Abstract

The London penetration depth, $\lambda (T)$, was measured in a single crystal V${}_3$Si. The superfluid density obtained from this measurement shows a distinct signature of two almost decoupled superconducting gaps. This alone is insufficient to distinguish between $s_{\pm }$ and $s_{++}$ pairing states, but it can be achieved by studying the effect of a controlled non-magnetic disorder on the superconducting transition temperature, $T_c$. For this purpose, the same ${\text{V}}_3\text{Si}$ crystal was sequentially irradiated by 2.5 MeV electrons three times, repeating the measurement between the irradiation runs. A total dose of 10 C/cm${}^2$ ($6.24\times 10^{19}$ electrons/${\text{cm}}^2$) was accumulated, for which $T_c$ has changed from 16.4 K in a pristine state to 14.7 K (9.3 $\%$). This substantial suppression is impossible for a single isotropic gap, but also it is not large enough for a sign-changing $s_{\pm }$ pairing state. Our electronic band-structure calculations show how five bands crossing the Fermi energy can be naturally grouped to support two effective gaps, not dissimilar from the iron pnictides physics. We analyze the results using two-gap models for both, $\lambda (T)$ and $T_c$, which describe the data very well. Thus, the experimental results and theoretical analysis provide strong support for an $s_{++}$ superconductivity with two unequal gaps, ${\Delta }_1\left(0\right)\approx 2.53\text{meV}$ and ${\Delta }_2\left(0\right)\approx 1.42\text{meV}$, and a very weak inter-band coupling in ${\text{V}}_3\text{Si}$ superconductor.

References in corpus (8)

• Magnetic Penetration Depth in Unconventional Superconductors
• Superfluid density and specific heat within self-consistent scheme for two-band superconductor
• Disorder-induced topological change of the superconducting gap structure in iron pnictides
• Microwave Response of V3Si Single Crystals: Evidence for Two-Gap Superconductivity
• Meissner-London susceptibility of superconducting right circular cylinders in an axial magnetic field
• Meissner-London state in anisotropic superconductors of cuboidal shape
• Magnetic penetration-depth measurements of a suppressed superfluid density of superconducting Ca${}_{0.5}$Na${}_{0.5}$Fe${}_2$As${}_2$ single crystals by proton irradiation
• Effect of controlled artificial disorder on the magnetic properties of EuFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$ ferromagnetic superconductor

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• Effects of 3 MeV Proton Irradiation on Superconductivity and CDW in 2H-NbSe2 Single Crystals
• Anisotropic multiband superconductivity in 2M-WS${}_2$ probed by controlled disorder
• Slope of the upper critical field at $T_c$ in two-band superconductors with non-magnetic disorder: $s_{++}$ superconductivity in ${\text{Ba}}_{1-x}{\text{K}}_x{\text{Fe}}_2{\text{As}}_2$
• Decoupled interband pairing in a bilayer iron-based superconductor evidenced by ultrahigh-resolution ARPES
• Enhancement of $J$${}_c$ by Proton Irradiation in HgBa${}_2$Ca${}_2$Cu${}_3$O${}_8$${}_{+}$${}_{\delta }$ Single Crystals