通过铁磁交换增强二维电子气的Edelstein效应
Boosting the Edelstein effect of two-dimensional electron gases by ferromagnetic exchange
AI总结：
本研究针对SrTiO₃二维电子气室温Edelstein效应较弱的问题，通过在紧束缚模型中引入面外塞曼项模拟铁磁交换耦合，发现其可将电荷自旋转换效率提升近一个数量级，揭示了效率随磁场的非单调变化源于交换耦合与Rashba相互作用的竞争。
摘要：
钛酸锶（SrTiO$_3$）二维电子气（2DEGs）具有破缺的空间反演对称性，且存在有限的Rashba自旋轨道耦合。这使得电荷流与自旋流可通过正向和逆向Edelstein效应相互转换，该效应在低温下效率创纪录，但在室温下效果较为有限。本研究表明，使这类2DEGs具备铁磁性可将转换效率提升近一个数量级。我们从非磁性SrTiO$_3$ 2DEGs的实验能带结构出发，在紧束缚模型中引入面外塞曼项来模拟磁交换耦合。随后我们计算了内磁场增大时的能带结构与自旋织构，并采用半经典Boltzmann方法计算Edelstein效应。研究发现，转换效率首先随磁场增大显著上升，达到最大值后最终下降。这种磁场依赖性源于交换耦合与有效Rashba相互作用的竞争：能带对的劈裂增强会放大Edelstein效应，而面内Rashba型自旋织构的减弱则会削弱该效应。
英文摘要：
Strontium titanate (SrTiO$_3$) two-dimensional electron gases (2DEGs) have broken spatial inversion symmetry and possess a finite Rashba spin-orbit coupling. This enables the interconversion of charge and spin currents through the direct and inverse Edelstein effects, with record efficiencies at low temperature, but more modest effects at room temperature. Here, we show that making these 2DEGs ferromagnetic enhances the conversion efficiency by nearly one order of magnitude. Starting from the experimental band structure of non-magnetic SrTiO$_3$ 2DEGs, we mimic magnetic exchange coupling by introducing an out-of-plane Zeeman term in a tight-binding model. We then calculate the band structure and spin textures for increasing internal magnetic fields and compute the Edelstein effect using a semiclassical Boltzmann approach. We find that the conversion efficiency first increases strongly with increasing magnetic field, then shows a maximum and finally decreases. This field dependence is caused by the competition of the exchange coupling with the effective Rashba interaction. While enhancing the splitting of band pairs amplifies the Edelstein effect, weakening the in-plane Rashba-type spin texture reduces it.
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