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arXiv 1302.0550cond-mat.str-elcond-mat.mtrl-sci
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半金属磁体中强相互作用效应的决定性量子蒙特卡罗研究

Effects of Strong Interactions in a Half Metallic Magnet: a Determinant Quantum Monte Carlo Study

M. Jiang, W. E. Pickett, R. T. Scalettar

摘要:

半金属磁体具有带隙自旋通道和金属通道的能带结构,了解半金属磁体中电子-电子相互作用的影响不仅是一个重要的理论问题,而且对它们的潜在应用具有重要意义。在这里,我们使用决定性量子Monte Carlo研究现场哈伯德相互作用$U$,有限的温度,和外部(塞曼)磁场的双层紧束缚模型,这是一个半金属在没有相互作用的影响,通过计算的频谱密度,电导率,自旋极化载流子,和局部磁性。我们量化的影响$U$的热去极化的程度,并遵循相对带移和监测时,显着的间隙状态出现,其中每一个可以降低HM字符。对于这个模型,塞曼耦合诱导,在固定的粒子数,两个连续的转变:补偿半金属与自旋下降带隙$\rightarrow$金属铁磁体$\rightarrow$饱和铁磁绝缘体。然而,在大多数更相关的参数范围内,半金属性质对$U$相当稳健。

英文摘要:

Understanding the effects of electron-electron interactions in half metallic magnets (HMs), which have band structures with one gapped spin channel and one metallic channel, poses fundamental theoretical issues as well as having importance for their potential applications. Here we use determinant quantum Monte Carlo to study the impacts of an on-site Hubbard interaction $U$, finite temperature, and an external (Zeeman) magnetic field on a bilayer tight-binding model which is a half-metal in the absence of interactions, by calculating the spectral density, conductivity, spin polarization of carriers, and local magnetic properties. We quantify the effect of $U$ on the degree of thermal depolarization, and follow relative band shifts and monitor when significant gap states appear, each of which can degrade the HM character. For this model, Zeeman coupling induces, at fixed particle number, two successive transitions: compensated half-metal with spin-down band gap $\rightarrow$ metallic ferromagnet $\rightarrow$ saturated ferromagnetic insulator. However, over much of the more relevant parameter regime, the half-metallic properties are rather robust to $U$.

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