Physical Review X (Sep 2015)

Spin-Fluctuation-Induced Non-Fermi-Liquid Behavior with Suppressed Superconductivity in LiFe_{1−x}Co_{x}As

  • Y. M. Dai,
  • H. Miao,
  • L. Y. Xing,
  • X. C. Wang,
  • P. S. Wang,
  • H. Xiao,
  • T. Qian,
  • P. Richard,
  • X. G. Qiu,
  • W. Yu,
  • C. Q. Jin,
  • Z. Wang,
  • P. D. Johnson,
  • C. C. Homes,
  • H. Ding

DOI
https://doi.org/10.1103/PhysRevX.5.031035
Journal volume & issue
Vol. 5, no. 3
p. 031035

Abstract

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We study a series of LiFe_{1−x}Co_{x}As compounds with different Co concentrations by transport, optical spectroscopy, angle-resolved photoemission spectroscopy, and nuclear magnetic resonance. We observe 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 find 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 that 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.