2021/08/30 by Yuta Mizukami, Mizukami, Y., O. Tanaka +23
Materials Science · #FOS: Physical sciences #Iron-based superconductors research #Superconductivity (cond-mat.supr-con)
paper · pdf · doi:10.48550/arxiv.2108.13081
openalex publication_date 2021/08/30 · openalex created_date 2021/09/13 · openalex updated_date 2026/07/28
Electronic nematic states with broken rotational symmetry often emerge in correlated materials. In most iron-based superconductors, the nematic anisotropy is oriented in the Fe-Fe direction of the iron square lattice. Recently, a novel type of nematicity along the diagonal Fe-As direction has been suggested in heavily hole-doped AFe2As2 (A= Rb or Cs). However, the transport studies focusing on the fluctuations of such nematicity have provided controversial results regarding the presence of diagonal nematic order. Here we report high-resolution heat capacity measurements under in-plane field rotation in RbFe2As2. While the temperature dependence of specific heat shows no discernible anomaly associated with the nematic transition, the field-angle dependence of specific heat near the superconducting transition (at ∼ 2.8 K) reveals clear two-fold oscillations within the plane, providing thermodynamic evidence for the diagonal nematicity. Moreover, we find that Mössbauer spectroscopy sensitively probes the nematic transition at ∼ 50 K with no evidence of static magnetism. These results imply that the diagonal nematicity in RbFe2As2 has a unique mechanism involving charge degrees of freedom, having unusual thermodynamic properties of the transition.