Strongly fluctuating moments in the higherature magnetic superconductor RbEuFe4As4

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

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8 Citations (Scopus)

Abstract

The iron-based superconductor RbEuFe4As4 undergoes a magnetic phase transition deep in the superconducting state. We investigate the calorimetric response of RbEuFe4As4 single crystals of the magnetic and the superconducting phase and its anisotropy to in-plane and out-of-plane magnetic fields. Whereas the unusual cusplike anomaly associated with the magnetic transition is suppressed to lower temperatures for fields along the crystallographic c axis, it rapidly transforms to a broad shoulder shifting to higher temperatures for in-plane fields. We identify the cusp in the specific-heat data as a Berezinskii-Kosterlitz-Thouless transition with fine features caused by the three-dimensional effects. The higherature shoulder in high magnetic fields marks a crossover from a paramagnetically disordered to an ordered state. This observation is further supported by Monte Carlo simulations of an easy-plane two-dimensional Heisenberg model and a fourth-order higherature expansion, both of which agree qualitatively and quantitatively with the experimental findings.

Original languageEnglish
Article number180502
JournalPhysical Review B
Volume99
Issue number18
DOIs
Publication statusPublished - May 23 2019

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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    Willa, K., Willa, R., Bao, J. K., Koshelev, A. E., Chung, D. Y., Kanatzidis, M. G., Kwok, W. K., & Welp, U. (2019). Strongly fluctuating moments in the higherature magnetic superconductor RbEuFe4As4. Physical Review B, 99(18), [180502]. https://doi.org/10.1103/PhysRevB.99.180502