paper

Commensurate lattice distortion in the layered titanium oxypnictides Na $_{2}$ Ti $_{2} P n_{2}$ O ( $P n =$ As, Sb) determined by X-ray diffraction

arXiv:1604.07284 · doi:10.1103/PhysRevB.94.104515

Abstract

We report single crystal X-ray diffraction measurements on Na $_{2}$ Ti $_{2} P n_{2}$ O ( $P n$ = As, Sb) which reveal a charge superstructure that appears below the density wave transitions previously observed in bulk data. From symmetry-constrained structure refinements we establish that the associated distortion mode can be described by two propagation vectors, $q_{1} = (1/2, 0, l)$ and $q_{2} = (0, 1/2, l)$ , with $l = 0$ (Sb) or $l = 1/2$ (As), and primarily involves in-plane displacements of the Ti atoms perpendicular to the Ti--O bonds. The results provide direct evidence for phonon-assisted charge density wave order in Na $_{2}$ Ti $_{2} P n_{2}$ O and identify a proximate ordered phase that could compete with superconductivity in doped BaTi $_{2}$ Sb $_{2}$ O.

Commensurate lattice distortion in the layered titanium oxypnictides Na2​Ti2​Pn2​O (Pn= As, Sb) determined by X-ray diffraction

Abstract

Commensurate lattice distortion in the layered titanium oxypnictides Na $_{2}$ Ti $_{2} P n_{2}$ O ( $P n =$ As, Sb) determined by X-ray diffraction