Anisotropic upper critical field of pristine and proton-irradiated single crystals of the magnetically ordered superconductor RbEuFe$_4$As$_4$
| Autor: | Smylie, M. P., Koshelev, A. E., Willa, K., Willa, R., Kwok, W. -K., Bao, J. -K., Chung, D. Y., Kanatzidis, M. G., Singleton, J., Balakirev, F. F., Hebbeker, H., Niraula, P., Bokari, E., Kayani, A., Welp, U. |
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| Rok vydání: | 2019 |
| Předmět: | |
| Zdroj: | Phys. Rev. B 100, 054507 (2019) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevB.100.054507 |
| Popis: | We present a study of the upper critical field, H$_{c2}$, of pristine and proton-irradiated RbEuFe$_4$As$_4$ crystals in pulsed magnetic fields of up to 65 T. The data for H$_{c2}$ reveal pronounced downwards curvature, particularly for the in-plane field orientation, and a superconducting anisotropy that decreases with decreasing temperature. These features are indicative of Pauli paramagnetic limiting. For the interpretation of these data, we use a model of a clean single-band superconductor with an open Fermi surface in the shape of a warped cylinder, which includes strong paramagnetic limiting. Fits to the data reveal that the in-plane upper critical field is Pauli paramagnetic limited, while the out-of-plane upper critical field is orbitally limited and that the orbital and paramagnetic fields have opposite anisotropies. A consequence of this particular combination is the unusual inversion of the anisotropy, $H_{c2}^{ab} < H_{c2}^c$, of the irradiated sample at temperatures below 10 K. The fits also yield an in-plane Maki parameter, $\alpha_M^{110} \approx$ 2.6, exceeding the critical value for the formation of the Fulde-Ferrell-Larkin-Ovchinnikov state. Nevertheless, the current measurements did not reveal direct evidence for the occurrence of this state. Comment: 10 pages (including references), 7 figures |
| Databáze: | arXiv |
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