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Temperature dependent anisotropy of the penetration depth and coherence length in MgB$_2

J. D. Fletcher·A. Carrington·O. J. Taylor·S. M. Kazakov·J. Karpinski
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Abstract

We report measurements of the temperature dependent anisotropies ($γ_λ$ and $γ_ξ$) of both the London penetration depth $λ$ and the upper critical field of MgB$_2$. Data for $γ_λ=λ_c/λ_a$ was obtained from measurements of $λ_{a}$ and $λ_c$ on a single crystal sample using a tunnel diode oscillator technique. $γ_ξ=H_{c2}^{\parallel c}/H_{c2}^{\bot c}$ was deduced from field dependent specific heat measurements on the same sample. $γ_λ$ and $γ_ξ$ have opposite temperature dependencies, but close to $T_c$ tend to a common value ($γ_λ\simeq γ_ξ=1.75\pm0.05$). These results are in good agreement with theories accounting for the two gap nature of MgB$_2$

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J. D. Fletcher, A. Carrington, O. J. Taylor, S. M. Kazakov, J. Karpinski. 2005-04-26. Temperature dependent anisotropy of the penetration depth and coherence length in MgB$_2. https://doi.org/10.1103/physrevlett.95.097005

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