基于DMRG的六方CrN纳米带锯齿形边缘磁有序分析
DMRG Analysis of Magnetic Order in the Zigzag Edges of Hexagonal CrN Nanoribbons
AI总结：
本研究结合密度泛函理论与DMRG方法分析六方CrN纳米带锯齿形边缘的磁有序，发现其具有半金属特性，一维自旋关联长度随温度骤降为零，且该边缘在两种掺杂下均为理想自旋过滤器。
摘要：
我们采用密度泛函理论结合密度矩阵重整化群（DMRG）方法，研究了六方CrN纳米带边缘的有限温度磁有序。此外，我们还基于半经典Boltzmann输运理论计算了纳米带中的自旋相关输运特性。研究发现，锯齿形边缘的能量低于扶手椅形边缘。CrN纳米带的锯齿形边缘呈现出与二维单层相同的半金属电子特性。锯齿形边缘上的局域电子态降低了自旋向下电子的电子带隙能量。我们将从头算得到的电子结果映射到包含次近邻交换相互作用项的有效一维Heisenberg自旋模型中。对于锯齿形纳米带，最近邻和次近邻磁交换作用分别约为10至12 meV/ Cr原子和-2至0 meV/ Cr原子。一维纳米带中的有限自旋关联长度随温度急剧下降至零。边缘处不存在长程自旋关联，这是未来室温二维自旋电子器件面临的实际缺陷。我们采用最大局域化Wannier函数进行能带插值，并通过半经典Boltzmann方程开展自旋相关输运计算。结果表明，CrN的锯齿形边缘在电子掺杂和空穴掺杂下均为理想的自旋过滤器。
英文摘要：
We investigate the finite temperature magnetic order at the edges of hexagonal CrN nanoribbons by using the density-functional theory combined with the density-matrix renormalization group method. Moreover, the spin-dependent transport in nanoribbons is calculated within the semi-classical Boltzmann transport theory. We find out that the zigzag edges have lower energy with respect to armchair edges. The zigzag edge of CrN nanoribbon shows half metallic electronic character which is the same as for the 2D monolayer. The localized electronic states on the zigzag edges reduce the electronic band gap energy for spin down electrons. The ab-initio electronic results are mapped into an effective 1D Heisenberg spin model up to the next nearest neighbor exchange interaction term. For zigzag ribbons, the nearest neighbor and next nearest neighbor magnetic exchange are around $10$ to $12$, and $-2$ to $0$~meV/Cr atom, respectively. The finite spin correlation length in 1D nanoribbons drops sharply to zero with temperature. The absence of long range spin correlations at the edges is a practical drawback for future room temperature 2D spintronic devices. The maximally localized Wannier functions are used for band interpolation and spin-dependent transport calculations by using the semi-classical Boltzmann equation. We show that zigzag edges of CrN are perfect spin filter under both electron and hole doping.
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