Superconductivity-induced transverse plasma mode and phonon anomaly in the $c$-axis response of the bilayer compound RbCa$_2$Fe$_4$As$_4$F$_2$

B. Xu; D. Munzar; A. Dubroka; E. Sheveleva; F. Lyzwa; P. Marsik; C. N. Wang; Z. C. Wang; G. H. Cao; C. Bernhard

doi:10.1103/PhysRevB.101.214512

paper

Superconductivity-induced transverse plasma mode and phonon anomaly in the $c$ -axis response of the bilayer compound RbCa $_{2}$ Fe $_{4}$ As $_{4}$ F $_{2}$

arXiv:2004.08819 · doi:10.1103/PhysRevB.101.214512

Abstract

With infrared spectroscopy we studied the out-of-plane ( $c$ -axis) response of the iron arsenide superconductor ACa $_{2}$ Fe $_{4}$ As $_{4}$ F $_{2}$ (A = Rb,Cs) which has a bilayer structure similar to the high $T_{c}$ cuprates YBa $_{2}$ Cu $_{3}$ O $_{7}$ (YBCO) and Bi $_{2}$ Sr $_{2}$ CaCu $_{2}$ O $_{8}$ (Bi2212). In analogy to the cuprates, we observe a superconductivity-induced transverse plasma mode (tPM) and a phonon anomaly that are both signatures of local electric field effects that arise from a large difference between the local conductivities in the intra- and inter-bilayer regions. Using a multilayer model developed for the cuprates, we obtain a good description of the $c$ -axis response and derive the local conductivities at $T ≃ T_{c}$ of $σ_{1}^{bl} (ω \to 0) ≃$ 1\,000 $Ω^{- 1} cm^{- 1}$ and $σ_{1}^{int} (ω \to 0) ≃$ 15 $Ω^{- 1} cm^{- 1}$ , respectively, that are similar to the ones previously found in underdoped YBCO. Different from the cuprates, we find no evidence of a normal state pseudogap in terms of a partial suppression of the low-energy electronic states that sets in already well above $T_{c}$ . There is also no clear sign of an onset of precursor superconducting pairing correlations well above $T_{c} ≃$ 30~K. This highlights that the pseudogap and the precursor superconducting pairing well above $T_{c}$ are unique features of the cuprates with their strong electronic correlations and, for example, not just the result of a strongly anisotropic electronic response due to the layered crystal structure.

10 pages, 8 figures

References in corpus (9)

Cited by in corpus (1)

Evidence of electron interaction with an unidentified bosonic mode in superconductor CsCa $_{2}$ Fe $_{4}$ As $_{4}$ F $_{2}$

Superconductivity-induced transverse plasma mode and phonon anomaly in the c-axis response of the bilayer compound RbCa2​Fe4​As4​F2​

Abstract

References in corpus (9)

Cited by in corpus (1)

Superconductivity-induced transverse plasma mode and phonon anomaly in the $c$ -axis response of the bilayer compound RbCa $_{2}$ Fe $_{4}$ As $_{4}$ F $_{2}$