Influence of In-induced resonant level on the normal-state and superconducting properties of Sn1.03Te

Normal-state transport properties (2-300 K) of the polycrystalline series Sn1.03-delta-xInx Te (0 <= x <= 0.07; 0.0025) were investigated by means of electrical resistivity, thermopower, Hall effect, and thermal conductivity measurements. The distortion of the valence-band structure by the In-induced resonant level (RL) has a profound influence on the evolution of the normal-state properties with x and on the emergence of superconductivity evidenced by specific-heat measurements down to 0.35 K. In addition to a nearly 40-fold increase in the residual electrical resistivity rho(0) on going from x = 0.0 to 0.05, the thermopower alpha shows a nonlinear, complex behavior as a function of both temperature and x. While Hall measurements indicate a dominant holelike response across the entire composition and temperature ranges, alpha changes sign below about 100 K and remains negative down to 5 K for 0.0015 <= x <= 0.0045. Additional measurements under magnetic fields mu H-0 of up to 14 T further shows that alpha(mu H-0) gradually shifts towards positive values, suggestive of a dominant holelike contribution to alpha. Superconductivity emerges for x = 0.02 at a critical temperature T-c = 0.67 K, with T-c increasing with x to reach 1.73 K for x = 0.07. The variations in the superconducting parameters with x, notably the specific-heat jump at T-c, confirm the results reported in prior studies and suggests a nontrivial role of the RL on the electron-phonon coupling strength. The striking similarities between this series and the canonical resonant system Pb1-xTlx Te provide an excellent experimental opportunity to gain a deeper understanding of the close interplay between resonant level, anomalous transport properties, and superconductivity.

Automated summary

The study investigates the normal-state transport properties and superconductivity of the Sn1.03-delta-xInxTe alloy. It finds that the distortion of the valence-band structure by the In-induced resonant level has a profound influence on the material's properties and the emergence of superconductivity.