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

• Published in: ACS nano Vol. 8; no. 3; pp. 2077 - 2086
• Main Authors: Mishra, Sukhada, Song, Kai, Ghosh, Kartik C, Nath, Manashi
• Format: Journal Article
• Language: English
• Published: American Chemical Society 25.03.2014
• Subjects: FeSe nanostructures; FeSe nanoparticles; T c enhancement; interfacial pressure
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/nn404262v

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-Pd16Se15–Au nanoparticle and sharing an interface with Pd17Se15. 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 Pd17Se15 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.