Superconductivity in monocrystalline YNiSi3 and LuNiSi3

Abstract

We report the discovery of bulk superconductivity in the ternary intermetallics YNiSi 3 and LuNiSi 3. High-quality single crystals were grown via the Sn-flux method and studied using magnetization, specific-heat, and resistivity measurements at low temperatures. The critical temperatures obtained from these different techniques are in very good agreement and yield T c = 1.36(3) K and T c = 1.61(2) K for YNiSi 3 and LuNiSi 3 , respectively. Magnetization measurements indicate that both compounds are among the rare cases where type-I superconductivity occurs in a ternary intermetallic, however, the jump in the specific heat at the transition is lower than the value expected from BCS theory (C el /γ n T c = 1.43) in both materials and is equal to 1.14(9) and 0.71(5) for the Y and Lu compounds, respectively. Resistivity measurements exhibit sharp transitions but with critical fields μ 0 H c (0) (≈0.05 T for YNiSi 3 and ≈0.08 T for LuNiSi 3) considerably higher than those obtained from the magnetization and specific heat (≈0.01 T). First-principles density functional theory calculated electronic structure shows that these compounds have highly anisotropic and complex Fermi surfaces with one electronic and two holelike branches. One hole branch and the electron branch have a large cylindrical topology connecting the first Brillouin-zone boundaries, the former being built up by the hybridization of Y(Lu) d, Ni d, and Si p states, and the latter being built up by Ni d and Si p states. The calculated phononic structures indicate that the coupling of the Y(Lu), Ni d, and Si p electrons in the low-lying optical phonon branches is responsible for the formation of Cooper pairs and the observed superconducting state. Therefore, these compounds can be classified as anisotropic three-dimensional metals with multiband superconducting ground states in the weak-coupling regime.

Anisotropic superconductivity and unusually robust electronic critical field in single crystal La7Ir3

“…An enhancement in the upper critical fields obtained from resistivity measurements is also seen in several other NCS superconductors including BeAu [35], BiPd [36], LaRhSi 3 [37], BaPtSi 3 [38], LuNiSi 3 [39], YNiSi 3 [39], LaPdSi 3 [40], and LaPtSi 3 [40]. The materials listed above differ from La 7 Ir 3 as they are type-I or marginal type I/II superconductors, with upper critical fields between 10 and 100's of mT, whereas La 7 Ir 3 is clearly type-II with a bulk critical field, H c2 (0), an order of magnitude higher.…”

Anisotropic superconductivity and unusually robust electronic critical field in single crystal La$_{7}$Ir$_{3}$

“…LuNiSi 3 [39], YNiSi 3 [39], LaPdSi 3 [40] and LaPtSi 3 [40]. The materials listed above differ from La 7 Ir 3 as they are type-I or marginal type I/II superconductors, with upper critical fields between 10 and 100's of mT, whereas La 7 Ir 3 is clearly type-II with a bulk critical field, H c2 (0), an order of magnitude higher.…”

Diversity in Crystal Structure and Physical Properties of RETX3 (RE – Rare Earth, T – Transition Metal, X – Main Group Element) Intermetallics

“…Intermetallic compounds with the composition RETX 3 ( RE – Rare Earth, T – Transition metals, X – Group 13–15 elements, except non‐metals) have been studied extensively because of their structural diversity, [1,2] which leads to interesting physical properties [3–5] . The presence of 4 f electrons in RE and the d ‐electrons in T and their interaction favors the generation of interesting magnetic and electronic properties such as ferromagnetism, antiferromagnetism, [6–10] spin‐glass, [11] Kondo behavior, [8,12,13] heavy fermion behavior, [14,15] mixed valence, [16–18] and superconductivity [7,19–24] . Along with physical properties some solid‐state structural transformation, [18] narrow band gap semiconductor [16] The highly localized 4 f electrons in rare‐earth atoms in “many” intermetallic compounds [6,25–28] .…”