Superconductivity in 122 antimonide SrPt₂Sb₂

Abstract

The crystal structure, superconducting properties, and electronic structure of a novel superconducting 122-type antimonide, BaPt 2 Sb 2 , have been investigated by measurements of powder X-ray diffraction patterns, electrical resistivity, ac magnetic susceptibility, specific heat as well as ab-initio calculations. This material crystallizes in a new-type of monoclinic variant of the CaBe 2 Ge 2 -type structure, in which Pt 2 Sb 2 layers consisting of PtSb 4 tetrahedra and Sb 2 Pt 2 layers consisting of SbPt 4 tetrahedra are stacked alternatively and Ba atoms are located between the layers.Measurements of electrical resistivity, ac magnetic susceptibility and specific heat revealed that BaPt 2 Sb 2 is a superconducting material with a T C of 1.8 K. The electronic heat capacity coefficient γ n and Debye temperature θ D were 8.6(2) mJ/mol K 2 and 146(4) K, where the figures in parentheses represent the standard deviation. The upper critical field µ 0 H C2 (0) and the Ginzburg-Landau coherent length ξ(0) were determined to be 0.27 T and 35 nm. Calculations showed that it has two three-dimensional Fermi surfaces (FSs) and two two-dimensional FSs, leading to anisotropic transport properties. The d-states of the Pt atoms in the Pt 2 Sb 2 layers mainly contribute to N(E F ). A comparison between experimental and calculated results indicates that BaPt 2 Sb 2 is a superconducting material with moderate coupling.

Possibility of charge density wave transition in a SrPt2Sb2superconductor

“…This is consistent with optical conductivity results in SrPt 2 As 2 [24] and the quasi-nesting features obtained by band structure calculations in SrPt 2 As 2 [26]. The negative curvature of the electrical resistivity temperature dependence (d 2 ρ/dT 2 < 0) [24,25,20,32,27] indicates strong electron-phonon interaction [34,35,36]. These results suggest that the CDW instability originates from momentum-dependent electron-phonon coupling.…”

“…The structure was first reported by Imre et al [23] to be a CaBe 2 Ge 2 -type structure at room temperature. In contrast, the XRD pattern reported by Imai et al [27] clearly demonstrated that SrPt 2 Sb 2 has not a tetragonal structure, but a lower symmetrical structure. However, the details of the structure in both phases and the magnetic properties near T = T 0 have yet to be identified.…”

“…In SrPt 2 Sb 2 , the coexistence of CDW and superconductivity is expected, as with SrPt 2 As 2 , while the coexistence of both phenomena is still unclear. It was reported that SrPt 2 Sb 2 exhibits superconductivity at T c = 2.1 K. Electrical resistivity measurements indicated a firstorder phase transition at T 0 ∼ 270 K [27], which implies a CDW transition. The structure was first reported by Imre et al [23] to be a CaBe 2 Ge 2 -type structure at room temperature.…”

Superconductivity in 122-Type Pnictides without Iron

“…ThCr 2 Si 2 -type structure has been found in SrNi 2 As 2 , LaRu 2 P 2 , and SrPd 2 As 2 , etc. [6,7,10,11,15,17,23,24,29] [18,19]. Structural phase transition is found in BaNi 2 As 2 from a high-temperature tetragonal phase to a low-temperature triclinic phase at T = 130 K [30].…”

“…On the other hand, SC is also observed in other 122-type compounds formulated with AT 2 Pn 2 (A = alkaline-earth or rare-earth; T = transition metals; Pn = P, As or Sb) without iron [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. It has been reported that these 122-compounds show a variety of interesting phenomena, such as SC [1], heavy fermion [26], densed Kondo behavior [27], coexistence of SC and anti-ferromagnetism (AFM)/ferromagnetism (FM) /spin-density-wave (SDW) or charge density wave (CDW) [1,13,28].…”