Crystallographic features of a low-temperature- tetragonal structure in La2-xBaxCuO4

Abstract Crystallographic features of both a low-temperature-tetragonal (LTT) structure and a related structural transition in La 1.875 Ba 0.125 CuO 4 have been examined by means of electron diffraction in a temperature range between room temperature and about 15 K. There exist two types of diffraction spots in electron diffraction patterns taken from La 1.875 Ba 0.125 CuO 4 at 16 K. One is a 100-type forbidden spot which shows that the oxide has the LTT structure. The other is a superlattice spot located at h 2 k 2 0 , the X point. From a calculated band structure [Krakauer et al. , Phys. Rev. B47 , 1002(1993)], it seems that the superlattice spot is an indication of the appearance of a charge density wave in the LTT structure.