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.

arXiv comment5 pages, 4 figures

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Cited by in corpus (9)

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• Double stage nematic bond-ordering above double stripe magnetism: application to BaTi${}_2$Sb${}_2$O
• Superconductivity in titanium-based pnictide oxide compounds
• Photoemission study of the electronic structure and charge density waves of Na2Ti2Sb2O
• Commensurate lattice distortion in the layered titanium oxypnictides Na${}_2$Ti${}_{2}P{n}_2$O ($Pn=$ As, Sb) determined by X-ray diffraction
• New phase transition in Na${}_2$Ti${}_2$As${}_2$O revealed by Raman scattering
• Exotic phase transition and superconductivity in layered titanium-oxypnictides implied by a computational phonon analysis
• Revealing the hidden order in BaTi2As2O via nuclear magnetic resonance
• Two superconducting phases and their characteristics in layered BaTi2(Sb1-xBix)2O with x=0.16