Formation of the density wave energy gap in Na${}_2$Ti${}_2$Sb${}_2$O: an optical spectroscopy study

Abstract

We performed optical spectroscopy measurement on single crystals of Na${}_2$Ti${}_2$Sb${}_2$O, which is the parent compound for the newly discovered Ti-based superconductors. The study reveals significant spectral change across the phase transition at 114 K and formation of a density-wave type energy gap. The opening of the gap removes most part of the free carrier spectral weight and causes a dramatic reduction of the carrier scattering rate. The ratio of 2$\Delta /k_B{T}_s\approx$14 is considerably larger than the mean-field value based on the weak-coupling BCS theory. The study also reveals a weak correlation effect in the titanium oxypnictides.

5 pages, 4 figures

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Cited by in corpus (3)

• Superconductivity in titanium-based pnictide oxide compounds
• Photoemission study of the electronic structure and charge density waves of Na2Ti2Sb2O
• Two superconducting phases and their characteristics in layered BaTi2(Sb1-xBix)2O with x=0.16