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

DOI: 10.1103/PhysRevB.94.104515 DOI Help

Authors: N. R. Davies (University of Oxford) , R. D. Johnson (University of Oxford) , A. J Princep (University of Oxford) , L. A. Gannon (University of Oxford) , J.-Z. Ma (Chinese Academy of Science; Swiss Light Source) , T. Qian (Institute of Physics, Chinese Academy of Science; Collaborative Innovation Center of Quantum Matter, Beijing) , P. Richard (Institute of Physics, Chinese Academy of Science; Collaborative Innovation Center of Quantum Matter, Beijing) , H. Li (Chinese Academy of Science) , M. Shi (Swiss Light Source) , H. Nowell (Diamond Light Source) , P. J. Baker (ISIS Facility) , Y. G. Shi (Institute of Physics, Chinese Academy of Science) , H. Ding (Institute of Physics, Chinese Academy of Science; Collaborative Innovation Center of Quantum Matter, Beijing) , J. Luo (Institute of Physics, Chinese Academy of Science) , Y. F. Guo (University of Oxford; ShanghaiTech University) , A. T. Boothroyd (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review B , VOL 94

State: Published (Approved)
Published: September 2016
Diamond Proposal Number(s): 10108

Abstract: We report single-crystal x-ray-diffraction measurements on Na 2 Ti 2 Pn 2 O(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 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. We also present angle-resolved photoemission spectroscopy measurements, which show band folding and backbending consistent with a density wave with the same wave-vectors q 1 and q 2 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 Na 2 Ti 2 Pn 2 O and fully characterize a proximate ordered phase that could compete with superconductivity in doped BaTi 2 Sb 2 O.

Journal Keywords: Charge density waves; Crystal symmetry; Nesting; Superconductivity; Superconductors; Angle-resolved photoemission spectroscopy; Crystal structures; Crystallography; Muon spin resonance; Photoemission spectroscopy; X-ray diffraction

Subject Areas: Materials, Physics


Instruments: I19-Small Molecule Single Crystal Diffraction

Other Facilities: SIS at Swiss Light Source; PGM at Synchrotron Radiation Center

Added On: 18/11/2016 13:50

Discipline Tags:

Superconductors Quantum Materials Physics Hard condensed matter - structures Materials Science

Technical Tags:

Diffraction Single Crystal X-ray Diffraction (SXRD)