Abstract
A series of LiFe$_{1-x}$Co$_{x}$As compounds with different Co concentrations have been studied by transport, optical spectroscopy, angle-resolved photoemission spectroscopy and nuclear magnetic resonance. We observed a Fermi liquid to non-Fermi liquid to Fermi liquid (FL-NFL-FL) crossover alongside a monotonic suppression of the superconductivity with increasing Co content. In parallel to the FL-NFL-FL crossover, we found that both the low-energy spin fluctuations and Fermi surface nesting are enhanced and then diminished, strongly suggesting that the NFL behavior in LiFe$_{1-x}$Co$_{x}$As is induced by low-energy spin fluctuations which are very likely tuned by Fermi surface nesting. Our study reveals a unique phase diagram of LiFe$_{1-x}$Co$_{x}$As where the region of NFL is moved to the boundary of the superconducting phase, implying that they are probably governed by different mechanisms.
Highlights
We study a series of LiFe1−xCoxAs compounds with different Co concentrations by transport, optical spectroscopy, angle-resolved photoemission spectroscopy, and nuclear magnetic resonance
In parallel to the FL-NFL-FL crossover, we find that both the low-energy spin fluctuations and Fermi surface nesting are enhanced and diminished, strongly suggesting that the NFL behavior in LiFe1−xCoxAs is induced by low-energy spin fluctuations that are very likely tuned by Fermi surface nesting
Through a combined study of transport, optical spectroscopy, angle-resolved photoemission spectroscopy (ARPES), and NMR on LiFe1−xCoxAs, we find that while superconductivity is monotonically suppressed with increasing Co concentration, the transport and optical properties reveal a prominent FL-NFL-FL crossover that closely follows the doping evolution of low-energy spin fluctuations (LESFs) and Fermi surfaces (FSs) nesting
Summary
High-quality single crystals of LiFe1−xCoxAs are grown with the self-flux method. The precursor of Li3As is prepared by sintering Li foil and an As lump at about 700 °C for 10 h in a Ti tube filled with Ar atmosphere. Fe1−xCoxAs is prepared by mixing the Fe, Co, and As powders thoroughly, and sealed in an evacuated quartz tube, and sintered at 700 °C for 30 h. The Li3As, Fe1−xCoxAs, and As powders are mixed according to the elemental ratio LiðFe1−xCoxÞ0.3As. The mixture is put into an alumina oxide tube and subsequently sealed in a Nb tube and placed in a quartz tube under vacuum. The entire process of preparing the starting materials and the evaluation of the final products are carried out in a glovebox purged with high-purity Ar gas
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