The new misfit compound (BiSe)1.15(TiSe2)2 and the role of dimensionality in the Cux(BiSe)1+δ(TiSe2)n series

•Reports the structure and properties of the new misfit compound (BiSe)1.15(TiSe2)2.•The structure consists of a rock salt type BiSe layer and a double (TiSe2)2 layer.•The n=1, 2 misfits (BiSe)1+δ(TiSe2)n are found not to exhibit CDW transitions.•Evidence is presented that there is likely a low-lying CDW excited state.•The series Cux(BiSe)1+δ(TiSe2)2 does not superconduct, unlike CuxTiSe2.

The synthesis and physical properties of the new misfit compound (BiSe)1.15(TiSe2)2 are reported. Transmission electron microscopy and powder X-ray diffraction show that the structure consists of alternating rock-salt type BiSe layers and hexagonal (TiSe2)2 double layers. Resistivity, specific heat, and magnetization measurements show that it has metallic and diamagnetic behaviors. These results are interpreted and discussed in the context of the transition between single-layer (BiSe)1.13(TiSe2), which shows no charge density wave, and infinite-layered (bulk) 1T-TiSe2, which undergoes a charge density wave transition at T=202 K. Intercalation with copper, Cux(BiSe)1.15(TiSe2)2, (0≤x≤0.10) is also reported, but unlike CuxTiSe2, no superconductivity is observed down to T=0.05 K. Thus, the series Cux(BiSe)1+δ(TiSe2)n provides an effective approach to elucidate the impact of dimensionality on charge density wave formation and superconductivity.

Graphical abstractThe newly discovered misfit compound (BiSe)1.15(TiSe2)2 shown in the series (BiSe)1+δ(TiSe2)n.Figure optionsDownload full-size imageDownload as PowerPoint slide