Superconducting properties of the ternary boride YRh4B4

• Published in: Superconductor science & technology Vol. 33; no. 12
• Main Authors: Jatmika, Jumaeda, Maruyama, Hiroshi, Rahman, Md Shahidur, Sakai, Akito, Nakatsuji, Satoru, Iyo, Akira, Ebihara, Takao
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.12.2020
• Subjects: boride; moderately high; YRh
• ISSN: 0953-2048; 1361-6668
• DOI: 10.1088/1361-6668/abbb18

The low number of physical parameters for superconductivity has motivated researchers to perform bulk measurements in YRh4B4, discovered four decades ago, with superconducting transition temperature ( Tc) of approximately 11 K. We performed electrical resistivity, magnetic susceptibility, and specific heat measurements to investigate the superconducting properties of the ternary borides YRh4B4 with CeCo4B4-type tetragonal structure. The nearly single-phase YRh4B4 had a moderately high Tc of 10.6 K. The lower and upper critical fields were determined to be 1.5 and 32 kOe, respectively, by magnetic susceptibility and electrical resistivity measurements. The Ginzburg-Landau parameter κGL was approximately 4.35, which is greater than >1/2, implying that YRh4B4 is a type-II superconductor. Because of specific heat measurements, the Debye temperature ΘD, ΔC/γTc, and 2 Δ0/Tc were determined to be 505 K, 1.56, and 3.91, respectively, where the specific heat jump at Tc and the superconducting gap at 0 K are expressed by ΔC and Δ0. The electrical resistivity at low temperatures showed quadratic temperature dependence, and its coefficient A was determined to be 0.004426 µΩ· cm K−2, indicating a large density of states at Fermi energy. The electron-phonon coupling constant λel-ph was derived to be 0.69. These results strongly suggest that YRh4B4 is a conventional s-wave superconductor described by the Bardeen-Cooper-Shriefer theory, and that the moderately high- Tc in YRh4B4 is attributable to a high ΘD due to vibrations of boron with a light mass and a large A-value originating from the large density of states at Fermi energy. These results will facilitate microscopic investigations and provide clues to develop a novel high- Tc metal superconductor.