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首页> 外文期刊>Physical review >Superconductivity from a non-Fermi-liquid metal: Kondo fluctuation mechanism in slave-fermion theory
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Superconductivity from a non-Fermi-liquid metal: Kondo fluctuation mechanism in slave-fermion theory

机译：非热液态金属的超导性：奴隶费米子理论中的近藤波动机制

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We propose Kondo fluctuation mechanism of superconductivity, differentiated from the spin-fluctuation theory as the standard model for unconventional superconductivity in the weak-coupling approach. Based on the U(1) slave-fermion representation of an effective Anderson lattice model, where localized spins are described by the Schwinger boson theory and hybridization or Kondo fluctuations weaken antiferromagnetic correlations of localized spins, we found an antiferromagnetic quantum critical point from an antiferromagnetic metal to a heavy-fermion metal in our recent study. The Kondo-induced antiferromagnetic quantum critical point was shown to be described by both conduction electrons and fermionic holons interacting with critical spin fluctuations given by deconfined bosonic spinons with a spin quantum number 1/2. Surprisingly, such critical modes turned out to be described by the dynamical exponent z=3, giving rise to the well-known non-Fermi-liquid physics such as the divergent Griineisen ratio with an exponent 2/3 and temperature-linear resistivity in three dimensions. We find that the z=3 antiferromagnetic quantum critical point becomes unstable against superconductivity, where critical spinon excitations give rise to pairing correlations between conduction electrons and between fermionic holons, respectively, via hybridization fluctuations. Such two kinds of pairing correlations result in multigap unconventional superconductivity around the antiferromagnetic quantum critical point of the slave-fermion theory, where s-wave pairing is not favored generically due to strong correlations. We show that the ratio between each superconducting gap for conduction electrons Δ_c and holons Δ_f and the transition temperature T_c is 2Δ_c/T_c～9 and 2Δ_f/T_c～O(10~(-1)), remarkably consistent with CeCoIn_5. A fingerprint of the Kondo mechanism is emergence of two kinds of resonance modes in not only spin but also charge fluctuations, where the charge resonance mode at an antiferromagnetic wave vector originates from d-wave pairing of spinless holons. We discuss how the Kondo fluctuation theory differs from the spin-fluctuation approach.
机译：我们提出了超导的近藤起伏机制，它与自旋涨落理论不同，是弱耦合方法中非常规超导的标准模型。基于有效Anderson晶格模型的U（1）从-费米子表示，其中用Schwinger玻色子理论描述了局部自旋，并且杂交或Kondo涨落削弱了局部自旋的反铁磁相关性，我们从反铁磁发现了反铁磁量子临界点在我们最近的研究中，金属变成了重费米金属。证明了近藤感应的反铁磁量子临界点是由传导电子和铁氧体hol相互作用，并与自旋量子数为1/2的约束硼原子自旋给出的临界自旋波动相互作用。出乎意料的是，这种临界模式被动力学指数z = 3所描述，从而产生了众所周知的非费米-液物理，例如发散的Griineisen比，其指数为2/3，温度-线性电阻率为3。尺寸。我们发现z = 3反铁磁量子临界点变得对超导不稳定，其中临界的自旋子激发通过杂交涨落分别引起了传导电子之间和铁离子性电子之间的配对相关性。这两种配对相关性导致在奴隶费米子理论的反铁磁量子临界点附近出现多间隙非常规超导性，在这种情况下，由于强相关性，一般不赞成使用s波配对。我们发现，每个超导间隙的传导电子Δ_c和holonsΔ_f与转变温度T_c的比值为2Δ_c/ T_c〜9和2Δ_f/ T_c〜O（10〜（-1）），与CeCoIn_5显着一致。近藤机理的指纹不仅在自旋中而且在电荷起伏中都出现了两种共振模式，其中反铁磁波矢量处的电荷共振模式源自无旋子的d波对。我们讨论了近藤波动理论与自旋波动方法的不同之处。

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