Lattice distortion and charge density wave in Na2Ti2Sb2O revealed by scanning tunnelling microscopy
Abstract
Na2Ti2Sb2O is a parent compound of the titanium-based oxypnictide superconductors. It possesses a phase transition at Ts = 115 K whose nature is still unclear. Here we report a scanning tunnelling microscopy/spectroscopy (STM/STS) study on a Na2Ti2Sb2O single crystal. We observe a lattice distortion on the Na-terminated surface below Ts, which displays a 2 × 2 modulation (superstructure). The modulation vectors q = (±0.5, 0) ? and (0, ±0.5) ? match well with the Fermi surface nesting vectors observed by angle resolved photoemission spectroscopy (ARPES), and also agree with recent X-ray diffraction. A partially opened gap-like feature is present in STS near EF. This evidences that the lattice distortion is driven by commensurate charge density wave order. Our results suggest the electron-phonon interaction is strong in Na2Ti2Sb2O and could be responsible for the superconductivity in titanium-based oxypnictides.
- Publication:
-
Philosophical Magazine
- Pub Date:
- March 2017
- DOI:
- 10.1080/14786435.2016.1269217
- Bibcode:
- 2017PMag...97..527R
- Keywords:
-
- STM;
- experimental;
- crystal;
- Na<SUB>2</SUB>Ti<SUB>2</SUB>Sb<SUB>2</SUB>O;
- charge density wave;
- lattice distortion