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arXiv · 1612.05540

Probing Bulk Superconducting Order Parameter in Ba(K)Fe$_2$As$_2$ by Four Complementary Techniques

A. V. Muratov·T. E. Kuzmicheva·A. V. Sadakov·S. Yu. Gavrilkin·D. A. Knyazev·S. A. Kuzmichev·Yu. A. Aleshchenko·A. A. Kordyuk·V. M. Pudalov·M. Abdel-Hafiez
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Abstract

Using four different experimental techniques, we performed comprehensive studies of the bulk superconductive properties of single crystals of the nearly optimally doped $Ba_{1-x}K_xFe_2As_2$ ($T_{c} \approx 36\,K$), a typical representative of the 122 family. We investigated temperature dependencies of the (i) specific heat $C_{el}(T)$, (ii) first critical magnetic field $H_{c1}(T)$, (iii) intrinsic multiple Andreev reflection effect (IMARE), and (iv) infrared reflectivity spectra. All data clearly show the presence of (at least) two superconducting nodeless gaps. The quantitative data on the superconducting spectrum obtained by four different techniques are consistent with each other: (a) the small energy gap $Δ_S(0) \approx 1.8 - 2.5\,meV$, and the large gap energy $Δ_L(0) \approx 9.5 - 11.3\,meV$ that demonstrates the signature of an extended s-wave symmetry ($\sim~33 \%$ in-plane anisotropy), (b) the characteristic ratio $2Δ_L/k_BT_C$ noticeably exceeds the BCS value.

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A. V. Muratov, T. E. Kuzmicheva, A. V. Sadakov, S. Yu. Gavrilkin, D. A. Knyazev, S. A. Kuzmichev, Yu. A. Aleshchenko, A. A. Kordyuk, V. M. Pudalov, M. Abdel-Hafiez. 2017-02-19. Probing Bulk Superconducting Order Parameter in Ba(K)Fe$_2$As$_2$ by Four Complementary Techniques. https://arxiv.org/abs/1612.05540

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