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Wide-range ideal 2D Rashba electron gas with large spin splitting in Bi2Se3/MoTe2 heterostructure (Bi2Se3/MoTe2异质结构中大自旋分裂的宽幅理想二维Rashba电子气)
发布时间:2017-02-20

Wide-range ideal 2D Rashba electron gas with large spin splitting in Bi2Se3/MoTe2 heterostructure (Bi2Se3/MoTe2异质结构中大自旋分裂的宽幅理想二维Rashba电子气)
Te-Hsien Wang & Horng-Tay Jeng
npj Computational Materials
 3, Article number: 5 (2017)
doi:10.1038/s41524-017-0011-5
Published online:09 February 2017
Abstract| Full Text | PDF OPEN

摘要:能实际应用的理想二维Rashba电子气(几乎所有的传导电子占据Rashba带)是应用半导体自旋电子的关键。本研究证实,这样带有大Rashba劈裂的理想二维Rashba电子气可以在拓扑绝缘体Bi2Se3薄膜上实现,该薄膜可在过渡金属硫化物MoTe2基板上按第一性原理计算结果指导生长得到。研究结果显示,Rashba带专处于MoTe2半导体带隙中一个较大的、约0.6  eV费米能级间隔中。如此宽幅的理想二维Rashba电子气具有大的自旋分裂,为实际利用Rashba效应提供了可能,之前从未做到。由于强自旋-轨道耦合,其Rashba分裂强度与重金属(如AuBi)表面的差不多,所引起的自旋进动距离小到10 nm左右。近Γ点的内(外)Rashba带平面内自旋极化最大约为70%60%)。室温下相干距离至少数倍于自旋进动长度,为采用自旋加工设备提供了良好的一致性。这种二维拓扑绝缘体/过渡金属硫化物异质结构中的理想Rashba带,具有能量范围宽、自旋进动长度短、相干距离长的特点,为室温下制造超薄纳米自旋电子器件(如Datta–Das自旋晶体管)铺平了道路。

Abstract: An application-expected ideal two-dimensional Rashba electron gas, i.e., nearly all the conduction electrons occupy the Rashba bands, is crucial for semiconductor spintronic applications. We demonstrate that such an ideal two-dimensional Rashba electron gas with a large Rashba splitting can be realized in a topological insulator Bi2Se3 ultrathin film grown on a transition metal dichalcogenides

Editorial Summary

2D electron gas for nanoscale spintronic deviceseditor (制造纳米自旋电子设备编辑器的二维电子气)

该研究通过计算揭示了纳米自旋电子晶体管在室温下工作的可能性。来自中国台湾清华大学的T. H. WangH. T. Jeng通过第一性原理计算,证实了一种理想的二维电子气(半导体自旋电子实现应用的关键)可在硒化铋超薄膜绝缘体中实现,该超薄膜用半导体MoTe2衬底、在室温下生长即可制备。超薄器件中形成的二维电子气表现出大的自旋分裂(两种状态的电子自旋间的分离),这正是晶体管之类的设备所需要的特性。采用电子自旋的电子器件来处理信息,用的是电子固有的自旋特性,而不象目前常规电子器件那样用的是电子的电荷特性。这会使设备在更小的空间内存储更多的数据,消耗更少的电能,使用更便宜的材料。 

Calculations reveal the potential for a nanoscale spintronic transistor that works at room temperature. T. H. Wang and H. T. Jeng of Taiwan’s National Tsing Hua University demonstrated through ‘first-principle’ calculations that an ideal two-dimensional electron gas, crucial for semiconductor spintronic applications, can be realized at room temperature in an insulating bismuth selenide ultrathin film grown on a semiconducting molybdenum titelluride substrate. The 2D electron gas formed in the ultrathin device demonstrated large ‘spin-splitting’, a separation between the two states of electron spin, which is needed for transistor-like devices. Spintronic devices use the intrinsic spinning property of electrons to process information instead of the electron charge used in conventional electronics. They could lead to devices that can store more data in a smaller space while consuming less power and using cheaper materials.

 
MoTe2 substrate through first-principle calculations. Our results show the Rashba bands exclusively over a very large energy interval of about 0.6 eV around the Fermi level within the MoTe2 semiconducting gap. Such a wide-range ideal two-dimensional Rashba electron gas with a large spin splitting, which is desirable for real devices utilizing the Rashba effect, has never been found before. Due to the strong spin–orbit coupling, the strength of the Rashba splitting is comparable with that of the heavy-metal surfaces such as Au and Bi surfaces, giving rise to a spin precession length as small as ~10 nm. The maximum in-plane spin polarization of the inner (outer) Rashba band near the Γ point is about 70% (60%). The room-temperature coherence length is at least several times longer than the spin precession length, providing good coherency through the spin processing devices. The wide energy window for ideal Rashba bands, small spin precession length, as well as long spin coherence length in this two-dimensional topological insulator/transition metal dichalcogenides heterostructure pave the way for realizing an ultrathin nano-scale spintronic device such as the Datta–Das spin transistor at room-temperature. 
 
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