Melting of vortex lattice in magnetic superconductor $\mathrm{Rb}\mathrm{Eu}\mathrm{Fe}_{4}\mathrm{As}_{4}$

A. E. Koshelev; K. Willa; R. Willa; M. Smylie; J. -K. Bao; D. Y. Chung; M. G. Kanatzidis; W. -K. Kwok; U. Welp

doi:10.1103/physrevb.100.094518

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arXiv · 1906.10236

Melting of vortex lattice in magnetic superconductor $\mathrm{Rb}\mathrm{Eu}\mathrm{Fe}_{4}\mathrm{As}_{4}$

A. E. Koshelev·K. Willa·R. Willa·M. Smylie·J. -K. Bao·D. Y. Chung·M. G. Kanatzidis·W. -K. Kwok·U. Welp

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Abstract

The iron-based superconductors are characterized by strong fluctuations due to high transition temperatures and small coherence lengths. We investigate fluctuation behavior in the magnetic iron-pnictide superconductor $\mathrm{Rb}\mathrm{Eu}\mathrm{Fe}_{4}\mathrm{As}_{4}$ by calorimetry and transport. We find that the broadening of the specific-heat transition in magnetic fields is very well described by the lowest-Landau-level scaling. We report calorimetric and transport observations for vortex-lattice melting, which is seen as a sharp drop of the resistivity and a step of the specific heat at the magnetic-field-dependent temperature. The melting line in the temperature/magnetic-field plane lies noticeably below the upper-critical-field line and its location is in quantitative agreement with theoretical predictions without fitting parameters. Finally, we compare the melting behavior of $\mathrm{Rb}\mathrm{Eu}\mathrm{Fe}_{4}\mathrm{As}_{4}$ with other superconducting materials showing that thermal fluctuations of vortices are not as prevalent as in the high-temperature superconducting cuprates, yet they still noticeably influence the properties of the vortex matter.

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A. E. Koshelev, K. Willa, R. Willa, M. Smylie, J. -K. Bao, D. Y. Chung, M. G. Kanatzidis, W. -K. Kwok, U. Welp. 2019-08-23. Melting of vortex lattice in magnetic superconductor $\mathrm{Rb}\mathrm{Eu}\mathrm{Fe}_{4}\mathrm{As}_{4}$. https://doi.org/10.1103/physrevb.100.094518

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