Hydrostatic high-pressure studies to 25 GPa on the model superconducting pnictide LaRu sub(2)P sub(2)

• Published in: Journal of physics. Conference series Vol. 500; pp. 1 - 6
• Main Authors: oozani, Neda, Lim, Jinhyuk, Schilling, James, Fotovat, Roxanna, Zheng, Chong, Hoffmann, Roald
• Format: Journal Article
• Language: English
• Published: 01.01.2014
• Subjects: Covalence; Diamonds; Hydrostatics; Phosphides; Phosphors; Planes; Superconductivity; Transition temperature
• ISSN: 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/500/3/032007

Prior to the discovery of the Fe-pnictides in 2008, the ruthenium phosphide LaRu sub(2)P sub(2) possessed the highest value of the superconducting transition temperature, T sub(c) approximately 4 K, in the entire pnictide family. Recently, there has been renewed interest in this compound in an effort to better understand why the Fe-pnictides have much higher values of T sub(c). In related phosphides superconductivity appears to only be present if the separation between the phosphor ions d sub(p-p) in neighboring RU sub(2)P sub(2) planes is greater than the critical value 2.8 A, too great for a P-P covalent bond to be formed. For example, in superconducting LaRu sub(2)P sub(2), the value of d sub(p-p) is 3.0 A. To test these ideas directly, we have carried out hydrostatic high-pressure studies on single-crystalline LaRu sub(2)P sub(2) in a diamond-anvil cell using He pressure medium to pressures as high as 25 GPa and temperatures as low as 1.5 K. We find that T sub(c) initially increases under pressure, but suddenly disappears above 2.1 GPa. Since d sub(p-p) decreases under pressure, the sudden disappearance of superconductivity is likely due to the formation of a covalent P-P bond between adjacent RU sub(2)P sub(2) planes and a possible structural phase transition.