The Remarkable Anisotropic Compressibility and Metallic Cr-Cr Chains in Topological Semimetal CrP₄ under High Pressure

Metal tetraphosphides (MP₄, M = 3d transition metals) exhibit the layered-structure character, in which the metal atom chains are sandwiched between the P₄²⁻ layers, and have attracted considerable interest due to the outstanding physical and chemical properties, such as good electrical conductivity and high lithium capacity. Herein, the CrP₄ single crystal is prepared using the high-pressure and high-temperature method via the 2000 ton Kawai-type multianvil apparatus at ShanghaiTech University (SHTech-2000). The structural modification under high pressure is investigated by synchrotron X-ray diffraction combined with diamond anvil cell techniques. CrP₄ shows remarkable axial anisotropic compressibility, in which the c-axis is more compressible than a- and b-axes. The formation of infinite chains of Cr-Cr metallic bonding in CrP₄ under high pressure enhances the electrical conductivity.