Superconductivity-induced transverse plasma mode and phonon anomaly in the c-axis response of the bilayer compound RbCa2Fe4As4F2
| Authors | |
|---|---|
| Year of publication | 2020 |
| Type | Article in Periodical |
| Magazine / Source | Physical Review B |
| MU Faculty or unit | |
| Citation | |
| Web | https://doi.org/10.1103/PhysRevB.101.214512 |
| Doi | http://dx.doi.org/10.1103/PhysRevB.101.214512 |
| Keywords | HIGH-TEMPERATURE SUPERCONDUCTORS; INFRARED CONDUCTIVITY; OPTICAL PHONONS; CHARGE DYNAMICS; PSEUDOGAP; YBA2CU3OY; STATE; GAP |
| Description | We studied the infrared response of polycrystalline samples of the iron arsenide superconductor (Rb, Cs)Ca2Fe4As4F2 (Rb,Cs-12442), which has a bilayer structure similar to the high-T-c cuprates YBa2Cu3O7 (YBCO) and Bi2Sr2CaCu2O8. The c-axis reflectivity spectra R-c have been derived from the reflectivity spectra of the polycrystalline samples R-poly and the in-plane spectrum of a corresponding Cs-12442 crystal R-ab using a geometrical averaging approach with R-c = 3R(poly) - 2R(ab). In analogy to the c-axis response of the cuprates, we observe a superconductivity-induced transverse plasma mode 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 interbilayer 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 similar or equal to T-c of sigma(bl)(1) (omega -> 0) similar or equal to 1000 Omega(-1)cm(-1) and sigma(int)(1) (omega -> 0) similar or equal to 15 Omega(-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 similar or equal to 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. |
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