Coexistence of superconductivity and density wave in $\mathrm{B}{\mathrm{a}}_2\mathrm{T}{\mathrm{i}}_2\mathrm{F}{\mathrm{e}}_2\mathrm{A}{\mathrm{s}}_4\mathrm{O}$: an optical spectroscopy study

Abstract

We performed an optical spectroscopy measurement on single crystals of $\mathrm{B}{\mathrm{a}}_2\mathrm{T}{\mathrm{i}}_2\mathrm{F}{\mathrm{e}}_2\mathrm{A}{\mathrm{s}}_4\mathrm{O}$, which is a newly discovered superconductor showing a coexistence of superconductivity and density wave order. The study reveals a spectral change related to the formation density wave energy gap below $T_{DW}\approx$125 K, leading to the removal of about half of the multiple Fermi surface sheets. The ratio of 2${\Delta }_{DW}$/$k_B{T}_{DW}\approx$ 11.9 is considerably larger than the mean-field value based on the weak-coupling BCS theory. At the lowest temperature in the superconducting state, we observed opening of superconducting energy gaps ${\Delta }_1(0)=3.4$ meV and ${\Delta }_2(0)=7.9$ meV. The properties of superconducting state in $\mathrm{B}{\mathrm{a}}_2\mathrm{T}{\mathrm{i}}_2\mathrm{F}{\mathrm{e}}_2\mathrm{A}{\mathrm{s}}_4\mathrm{O}$ are similar to that in $\mathrm{BaF}{\mathrm{e}}_{1.85}\mathrm{C}{\mathrm{o}}_{0.15}\mathrm{A}{\mathrm{s}}_2$.

5 pages, 5 figures

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Cited by in corpus (1)

• Optical spectroscopy study of charge density wave order in Sr${}_3$Rh${}_4$Sn${}_{13}$ and (Sr${}_{0.5}$Ca${}_{0.5}$)${}_3$Rh${}_4$Sn${}_{13}$