知社·今日

1861年，麦克斯韦构想了位移电流的概念，完善了电动力学定律，并使利用位移电流的器件得以实现。虽然近来致力于畴的研究蓬勃兴起，畴在化合物中的相应电导率也有探讨，但目前尚不清楚这种位移电流是否会在有畴铁系统中引起大的固有交流电流，同时人们也很难确定驱动直流畴壁导电的机制。来自美国阿肯色州立大学和俄罗斯南联邦大学的Sergey Prosandeev等使用数值模型表明，高频畴壁电导可能发生在多铁铋铁氧体中，铋铁氧体的畴壁具有较高的交流电导率，畴壁的固有物理性质决定了高频畴壁电导。根据他们的预测，这个畴壁导电机制可能为千兆赫电子系统的开发提供更强大的平台。

该文近期发表于npj Computational Materials 4:8(2018); doi:10.1038/s41524-018-0066-y。英文标题与摘要如下，点击阅读原文可以自由获取论文PDF。

Displacement Current in Domain Walls of Bismuth Ferrite

Sergey Prosandeev,Yurong Yang,Charles Paillard& L. Bellaiche

Abstract In 1861, Maxwell conceived the idea of the displacement current, which then made laws of electrodynamics more complete and also resulted in the realization of devices exploiting such displacement current. Interestingly, it is presently unknown if such displacement current can result in large intrinsic ac current in ferroic systems possessing domains, despite the flurry of recent activities that have been devoted to domains and their corresponding conductivity in these compounds. Here, we report first-principles-based atomistic simulations that predict that the transverse (polarization-related) displacement currents of 71° and 109° domains in the prototypical BiFeO3multiferroic material are significant at the walls of such domains and in the GHz regime, and, in fact, result in currents that are at least of the same order of magnitude than previously reported dc currents (that are likely extrinsic in nature and due to electrons). Such large, localized and intrinsic ac currents are found to originate from low-frequency vibrations at the domain walls, and may open the door to the design of novel devices functioning in the GHz or THz range and in which currents would be confined within the domain wall.

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