Enhancement of Superconducting T_c (33 K) by Entrapment of FeSe in Carbon Coated Au–Pd₁₇Se₁₅ Nanoparticles

FeSe has been an interesting member of the Fe-based superconductor family ever since the discovery of superconductivity in this simple binary chalcogenide. Simplicity of composition and ease of synthesis has made FeSe, in particular, very lucrative as a test system to understand the unconventional nature of superconductivity, especially in low-dimensional models. in this article we report the synthesis of composite nanoparticles containing FeSe nanoislands entrapped within an ent -FeSe-Pd ₁₆ Se ₁₅ –Au nanoparticle and sharing an interface with Pd ₁₇ Se ₁₅ . This assembly exhibits a significant enhancement in the superconducting T _c (onset at 33 K) accompanied by a noticeable lattice compression of FeSe along the <001> and <101> directions. the T _c in FeSe is very sensitive to application of pressure and it has been shown that with increasing external pressure T _c can be increased almost 4-fold. in these composite nanoparticles reported here, immobilization of FeSe on the Pd ₁₇ Se ₁₅ surface contributes to increasing the effect of interfacial pressure, thereby enhancing the T _c . the effect of interfacial pressure is also manifested in the contraction of the FeSe lattice (up to 3.8% in <001> direction) as observed through extensive high-resolution TEM imaging. the confined FeSe in these nanoparticles occupied a region of approximately 15–25 nm, where lattice compression was uniform over the entire FeSe region, thereby maximizing its effect in enhancing the T _c . the nanoparticles have been synthesized by a simple catalyst-aided vapor transport reaction at 800 °C where iron acetylacetonate and Se were used as precursors. Morphology and composition of these nanoparticles have been studied in details through extensive electron microscopy.