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Competition between superconductivity and magneticematic order as a source of anisotropic superconducting gap in underdoped Ba_(1-x)K_xFe_2As_2

机译:欠掺杂Ba_(1-x)K_xFe_2As_2中作为各向异性超导间隙源的超导和磁/向列序之间的竞争

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摘要

The in-plane London penetration depth Δλ(T) was measured using a tunnel diode resonator technique in single crystals of Ba_(1-x)K_xFe_2As_2 with doping levels x ranging from heavily underdoped, x = 0.16 (T_c = 7 K), to nearly optimally doped, x = 0.34 (T_c = 39 K). Exponential saturation of Δλ(T) in the T → 0 limit is found in optimally doped samples, with the superfluid density ρ_s(T) = [λ(0)/λ(T)]~2 quantitatively described by a self-consistent γ model with two nodeless isotropic superconducting gaps. As the doping level is decreased towards the extreme end of the superconducting dome at x = 0.16, the low-temperature behavior of Δλ(T) becomes nonexponential and is best described by the power law Δλ(T) ∝ T~2, characteristic of strongly anisotropic gaps. The change between the two regimes happens within the range of coexisting magneticematic order and superconductivity, x < 0.25, and is accompanied by a rapid rise in the absolute value of Δλ(T) with underdoping. This effect, characteristic of the competition between superconductivity and other ordered states, is very similar to but of significantly smaller magnitude than what is observed in the electron-doped Ba(Fe_(1-x)Co_x)_2As_2 compounds. Our study suggests that the competition between superconductivity and magneticematic order in hole-doped compounds is weaker than in electron-doped compounds, and that the anisotropy of the superconducting state in the underdoped iron pnictides is a consequence of the anisotropic changes in the pairing interaction and in the gap function promoted by both magnetic and nematic long-range orders.
机译:使用隧道二极管谐振器技术在Ba_(1-x)K_xFe_2As_2单晶中测量平面内伦敦穿透深度Δλ(T),掺杂水平x范围从重度低掺杂,x = 0.16(T_c = 7 K)几乎最佳掺杂,x = 0.34(T_c = 39 K)。在最优掺杂样品中,在T→0极限处发现了Δλ(T)的指数饱和,超流密度ρ_s(T)= [λ(0)/λ(T)]〜2用自洽γ定量描述。两个无节点各向同性超导间隙的模型。当掺杂水平在x = 0.16处朝超导圆顶的末端减小时,Δλ(T)的低温行为变为非指数行为,并且可以通过幂定律Δλ(T)∝ T〜2来最好地描述。强烈的各向异性缺口。两种状态之间的变化发生在共存的磁/向列和超导性范围内(x <0.25),并且伴随着掺杂不足,Δλ(T)的绝对值快速上升。这种效应是超导态与其他有序态之间竞争的特征,与在电子掺杂的Ba(Fe_(1-x)Co_x)_2As_2化合物中观察到的效应非常相似,但幅度明显较小。我们的研究表明,空穴掺杂化合物中的超导性与磁/向列序之间的竞争比电子掺杂化合物中的弱,并且在掺杂不足的铁素体中,超导态的各向异性是配对中各向异性变化的结果相互作用和间隙功能由磁和向列远距离命令促进。

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  • 来源
    《Physical review》 |2014年第1期|014517.1-014517.7|共7页
  • 作者单位

    Ames Laboratory, Ames, Iowa 50011, USA;

    Ames Laboratory, Ames, Iowa 50011, USA,Department of Physics & Astronomy, Iowa State University, Iowa 50011, USA;

    Ames Laboratory, Ames, Iowa 50011, USA;

    Ames Laboratory, Ames, Iowa 50011, USA;

    Department of Physics & Astronomy, Iowa State University, Iowa 50011, USA;

    Department of Physics & Astronomy, Iowa State University, Iowa 50011, USA;

    Departement de Physique & RQMP, Universite de Sherbrooke, Sherbrooke, Canada;

    Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures & Department of Physics, Nanjing University, Nanjing 210093, China;

    Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures & Department of Physics, Nanjing University, Nanjing 210093, China;

    School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA;

    Ames Laboratory, Ames, Iowa 50011, USA,Department of Physics & Astronomy, Iowa State University, Iowa 50011, USA;

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  • 正文语种 eng
  • 中图分类
  • 关键词

    pairing symmetries (other than s-wave); effects of crystal defects, doping and substitution;

    机译:配对对称性(s波除外);晶体缺陷;掺杂和取代的影响;

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