Heavy-impurity resonance, hybridization, and phonon spectral functions
Heavy-impurity resonance, hybridization, and phonon spectral functions
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DOI：
10.1103/physrevb.91.094307
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发表时间：
2015-03-31
影响因子：
3.7
通讯作者：
Berlijn, T.
中科院分区：
文献类型：
--
作者：
Delaire, O.;Al-Qasir, I. I.;Berlijn, T.
采用非弹性中子散射、输运测量和第一性原理模拟相结合的方法研究了Fe 1-xMxSi（x = 0，0. 02，0. 04，0. 1）中重代位杂质（M = Ir，Os）的振动行为.我们的INS测量单晶映射的四维动力学结构因子，S（Q，E），几个组成和温度。我们的研究结果表明，Ir和Os杂质导致形成一个弱色散共振振动模式，在能量范围内的声学声子分散体的FeSi主机。我们还表明，Ir掺杂，引入自由载流子，导致软化的原子间力常数相比，掺杂与Os，这是等电子的Fe。基于第一性原理的密度泛函理论模拟，我们通过引入声子自能的绿色函数模型分析了INS中的声子S（Q，E），并研究了大型超原胞中的无序诱导寿命.准粒子谱函数的计算揭示了共振模式和声学声子模式之间的杂化。我们的研究结果表明，主机声学色散与共振模式的强烈相互作用，可能导致观察到的晶格热导率的大抑制。
The vibrational behavior of heavy substitutional impurities (M = Ir, Os) in Fe1-xMxSi (x = 0,0.02,0.04,0.1) was investigated with a combination of inelastic neutron scattering (INS), transport measurements, and first-principles simulations. Our INS measurements on single crystals mapped the four-dimensional dynamical structure factor, S(Q, E), for several compositions and temperatures. Our results show that both Ir and Os impurities lead to the formation of a weakly dispersive resonance vibrational mode, in the energy range of the acoustic phonon dispersions of the FeSi host. We also show that Ir doping, which introduces free carriers, leads to softened interatomic force constants compared to doping with Os, which is isoelectronic to Fe. We analyze the phonon S(Q, E) from INS through a Green's-function model incorporating the phonon self-energy based on first-principles density functional theory simulations, and we study the disorder-induced lifetimes on large supercells. Calculations of the quasiparticle spectral functions in the doped system reveal the hybridization between the resonance and the acoustic phonon modes. Our results demonstrate a strong interaction of the host acoustic dispersions with the resonance mode, likely leading to the large observed suppression in lattice thermal conductivity.