Quasi-One-Dimensional Metallicity in Compressed CsSnI3

Low-dimensional metal halides exhibit strong structural and electronic anisotropies, making them candidates for accessing unusual electronic properties. Here, we demonstrate pressure-induced quasi-one-dimensional (quasi-1D) metallicity in delta-CsSnI3. With the application of pressure up to 40 GPa, the initially insulating delta-CsSnI3 transforms to a metallic state. Synchrotron X-ray diffraction and Raman spectroscopy indicate that the starting 1D chain structure of edge-sharing Sn-I octahedra in delta-CsSnI3 is maintained in the high-pressure metallic phase while the SnI6 octahedral chains are distorted. Our experiments combined with first-principles density functional theory calculations reveal that pressure induces Sn-Sn hybridization and enhances Sn-I coupling within the chain, leading to band gap closure and formation of conductive SnI6 distorted octahedral chains. In contrast, the interchain I...I interactions remain minimal, resulting in a highly anisotropic electronic structure and quasi-1D metallicity. Our study offers a high-pressure approach for achieving diverse electronic platforms in the broad family of lowdimensional metal halides.

Automated summary

By applying pressure, quasi-one-dimensional metallic properties were achieved in the three-dimensional metal halide CsSnI3. The pressure-induced hybridization between Sn-Sn and enhanced coupling between Sn-I within the chain resulted in band gap closure and the formation of conductive SnI6 distorted octahedral chains. Meanwhile, the minimal interactions between interchain I...I led to a highly anisotropic electronic structure.