Superconductivity and physical properties of strongly electron correlated compounds La n Ru 3n−1 B 2n (n = 1, 2, and 3)

We examined the physical properties of homologous La n Ru 3 n −1 B 2 n ( n = 1−3) series including a new compound of n = 2. All of these compounds showed strong electron-electron correlation characterized by large Wilson ratio. In contrast to LaRu 2 B 2 and La 2 Ru 5 B 4 that show normal metal behaviors down to 1.8 K, we discover La 3 Ru 8 B 6 is an intermediately coupled BCS superconductor with . The experimental and theoretical calculation results suggest that the emergence of superconductivity in La 3 Ru 8 B 6 can be attributed to the rather large density of states at E F when compared to other two compounds.