Coupled commensurate charge density wave and lattice distortion in Na2Ti2Pn2O (Pn = As,Sb) determined by x-ray diffraction and angle-resolved photoemission spectroscopy

Journal article

We report single-crystal x-ray-diffraction measurements on Na2Ti2Pn2O (Pn = 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 q1 = (1/2,0,l) and q2 = (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.We also present angle-resolved photoemission spectroscopy measurements, which show band folding and backbending consistent with a density wave with the samewave-vectors q1 and q2 associated with Fermi-surface nesting, and muon-spin relaxation data, which show no indication of spin density wave order. The results provide direct evidence for phonon-assisted charge density wave order in Na2Ti2Pn2O and fully characterize a proximate ordered phase that could compete with superconductivity in doped BaTi2Sb2O.

Authors: Davies, N; Johnson, R; Princep, A; Gannon, L; Ma, J

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Physical Society
• Journal: Physical Review B
• Volume: 94
• Publication date: 2016-09-19
• Acceptance date: 2016-08-30
• DOI: 10.1103/PhysRevB.94.104515
• ISSN: 2469-9950 and 2469-9969
• Language: English