Structure and physical properties of the misfit compounds (PbSe)1.16(TiSe2)m (m = 1, 2)

The single-crystalline misfit compounds (PbSe) 1.16 (TiSe 2 ) and (PbSe) 1.16 (TiSe 2 ) 2 have been successfully synthesized. The structure and physical properties of the two misfit compounds are systematically investigated. The former consists of one-layer TiSe 2 alternating stacking with double-layer PbSe, in contrast with the latter which owns double-layer TiSe 2 . Moreover, (PbSe) 1.16 (TiSe 2 ) 2 with two-layer TiSe 2 shows superconductivity at 2.3 K while (PbSe) 1.16 (TiSe 2 ) with one-layer TiSe 2 is non-superconducting. Anisotropic resistivity indicates much stronger anisotropy of (PbSe) 1.16 (TiSe 2 ) 2 than that of (PbSe) 1.16 (TiSe 2 ), suggesting much weaker inter-layer coupling and lower dimensionality in the former. Hall and Seebeck coefficients show a sign reversal for (PbSe) 1.16 (TiSe 2 ) at low temperature, which indicates the change of charge carrier type from electron-dominated to hole-dominated. The comparison of physical properties between the two misfit compounds suggests that the lack of superconductivity in (PbSe) 1.16 (TiSe 2 ) is related to the change of charge carrier type. Moreover, the reduction of dimensionality in (PbSe) 1.16 (TiSe 2 ) 2 may be helpful for the superconductivity.