Specific heat evidence for two-gap superconductivity in ternary-iron silicide Lu${}_2$Fe${}_3$Si${}_5$

Abstract

We report low-temperature specific heat studies on single-crystalline ternary-iron silicide superconductor Lu${}_2$Fe${}_3$Si${}_5$ with$T_c$ = 6.1 K down to $\sim T_c/20$. We confirm a reduced normalized jump in specific heat at $T_c$, and find that the specific heat divided by temperature $C/T$ shows sudden drop at $\sim T_c/5$ and goes to zero with further decreasing temperature. These results indicate the presence of two distinct superconducting gaps in Lu${}_2$Fe${}_3$Si${}_5$, similar to a typical two-gap superconductor MgB${}_2$. We also report Hall coefficients, band structure calculation, and the anisotropy of upper critical fields for Lu${}_2$Fe${}_3$Si${}_5$, which support the anisotropic multiband nature and reinforce the existence of two superconducting gaps in Lu${}_2$Fe${}_3$Si${}_5$.

5 pages, 5 figures