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arXiv 1602.06193cond-mat.str-el
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金属Rashba带中的螺旋电流

Helical currents in metallic Rashba strips

Ignacio J. Hamad, Claudio J. Gazza, Jose A. Riera

摘要:

研究了零温下Rashba自旋轨道耦合(RSOC)存在时金属平面带中螺旋电流的织构。在非相互作用的情况下,在没有外部电磁源的情况下,我们确定通过精确的数值对角化的单粒子哈密顿量,分布在整个带部分的这些Rashba螺旋电流(RHC)以及他们的符号振荡,作为一个函数的RSOC强度,带宽度,电子填充,和带边界条件。然后,我们研究了由Aharonov-Bohm通量引入到系统中的电荷电流的影响的情况下的环或由电压偏置的情况下的开放带。前者用变分蒙特卡罗方法研究,后者用含时密度矩阵重整化群方法研究。特别是对于由两个,三个和四个耦合链形成的条带,我们展示了这些RHC如何在存在这种感应电荷电流的情况下变化,以及它们在每条链上的自旋向上和自旋向下电子电流之间的差异,有助于解释整个条带的电荷电流分布,无论是自旋守恒还是自旋翻转类型。我们还预测了每个链上的极化电荷电流的外观。最后,我们表明,这些Rashba螺旋电流和它们的衍生功能仍然存在的现场哈伯德排斥,只要系统仍然是金属,在四分之一填充,甚至在半填充的莫特哈伯德金属绝缘体过渡发生大哈伯德排斥。

英文摘要:

We study the texture of helical currents in metallic planar strips in the presence of Rashba spin-orbit coupling (RSOC) on the lattice at zero temperature. In the noninteracting case, and in the absence of external electromagnetic sources, we determine by exact numerical diagonalization of the single-particle Hamiltonian, the distribution across the strip section of these Rashba helical currents (RHC) as well as their sign oscillation, as a function of the RSOC strength, strip width, electron filling, and strip boundary conditions. Then, we study the effects of charge currents introduced into the system by an Aharonov-Bohm flux for the case of rings or by a voltage bias in the case of open strips. The former setup is studied by variational Monte Carlo, and the later, by the time-dependent density-matrix-renormalization group technique. Particularly for strips formed by two, three and four coupled chains, we show how these RHC vary in the presence of such induced charge current, and how their differences between spin-up and spin-down electron currents on each chain, help to explain the distribution across the strip of charge currents, both of the spin conserving and the spin flipping types. We also predict the appearance of polarized charge currents on each chain. Finally, we show that these Rashba helical currents and their derived features remain in the presence of an on-site Hubbard repulsion as long as the system remains metallic, at quarter filling, and even at half-filling where a Mott-Hubbard metal-insulator transition occurs for large Hubbard repulsion.

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