Electronic structure of the BaTi$_2$As$_2$O parent compound of the   titanium based oxypnictide superconductor
  The electronic structure of BaTi2As2O, a parent compound of the newly discovered titanium-based oxypnictide superconductors, is studied by angle-resolved photoemission spectroscopy. The electronic structure shows multi-orbital nature and possible three-dimensional character. An anomalous temperature-dependent spectral weight redistribution and broad lineshape indicate the incoherent nature of the spectral function. At the density-wave-like transition temperature around 200 K, a partial gap opens at the Fermi patches. These findings suggest that BaTi2As2O is likely a charge density wave material in the strong interaction regime. 
H. C. Xu, M. Xu, R. Peng, Y. Zhang, Q. Q. Ge, F. Qin, M. Xia, J. J.   Ying, X. H. Chen, M. Arita, K. Shimada, M. Taniguchi, ...
cond-mat.supr-con cond-mat.str-el