A Study of Superconductivity in a Series of Strontium Platinum Phosphides

In this work, the superconductivity in a series of strontium platinum phosphides was investigated. Three compounds, SrPt3P, SrPt6P2, and SrPt10P4, the latter two of which we discovered, were synthesized and characterized. We studied SrPt3P(1-x)Six resistively, magnetically, and calorimetrically, and found an apparent non-scaling of the Tc with the density of states at the Fermi level N(EF) that can be attributed to a significant weakening of the electron-phonon interaction strength. We found superconductivity in the new structure type SrPt6P2 at Tc = 0.6 K and attribute the lower value of Tc to a weak coupling strength as evidenced by our specific heat measurement and analysis. Superconductivity at Tc = 1.4 K was found in another new structure type compound SrPt10P4 with structural building blocks reminiscent of those from both SrPt3P and SrPt6P2. In SrPt10P4, our specific heat and upper critical field Hc2 measurements indicate the opening of two superconducting gaps Delta1 and Delta2 below Tc. A method of comparing the contributions to superconductivity in different compounds by analysis of the specific heat is developed in which the contribution from the density of states at the Fermi level N(EF) is separated from that of the interaction strength V and is applied to gain insight into the factors driving the superconductivity in these compounds.Physics, Department o

High-K dielectric sulfur-selenium alloys.

Upcoming advancements in flexible technology require mechanically compliant dielectric materials. Current dielectrics have either high dielectric constant, K (e.g., metal oxides) or good flexibility (e.g., polymers). Here, we achieve a golden mean of these properties and obtain a lightweight, viscoelastic, high-K dielectric material by combining two nonpolar, brittle constituents, namely, sulfur (S) and selenium (Se). This S-Se alloy retains polymer-like mechanical flexibility along with a dielectric strength (40 kV/mm) and a high dielectric constant (K = 74 at 1 MHz) similar to those of established metal oxides. Our theoretical model suggests that the principal reason is the strong dipole moment generated due to the unique structural orientation between S and Se atoms. The S-Se alloys can bridge the chasm between mechanically soft and high-K dielectric materials toward several flexible device applications

Synthesis, Structure, and Superconductivity in the New-Structure-Type Compound: SrPt₆P₂

A metal-rich ternary phosphide, SrPt₆P₂, with a unique structure type was synthesized at high temperatures. Its crystal structure was determined by single-crystal X-ray diffraction [cubic space group <i>Pa</i>3̅; <i>Z</i> = 4; <i>a</i> = 8.474(2) Å, and <i>V</i> = 608.51(2) ų]. The structure features a unique three-dimensional anionic (Pt₆P₂)^2– network of vertex-shared Pt₆P trigonal prisms. The Sr atoms occupy a 12-coordinate (Pt) cage site and form a cubic close-packed (face-centered-cubic) arrangement, and the P atoms formally occupy tetrahedral interstices. The metallic compound becomes superconducting at 0.6 K, as evidenced by magnetic and resistivity measurements