Spin Lifetime in Ballistic Spin-Orbit Materials: Fundamental features unravelled

by Super User

ICN2 researchers Aron W. Cummings and ICREA professor Stephan Roche, from the Theoretical and Computational Nanoscience group report new insights on spin lifetime in ballistic spin-orbit materials. Their results have just been published in Physical Review Letters.

The understanding of spin transport in the ballistic limit of materials subjected to spin-orbit interaction is challenging but of high relevance for spintronics. Here we theoretically found that the spin lifetime is dictated by dephasing that arises from energy broadening plus a non-uniform spin precession. For the case of clean graphene, spin lifetimes are highly anisotropic and can be as low as a few nanoseconds, setting the ultimate limit for practical spin devices.

Since its initial application to two-dimensional electron gases, the Rashba source of spin-orbit coupling has been fundamental to the understanding of a variety of physical phenomena such as the intrinsic spin Hall effect, and to the design of novel types of spintronic devices such as the Datta-Das spin transistor. The Rashba spin-orbit interaction also plays an important role in the new class of 2D materials, including graphene and transition metal dichalcogenides. In these materials, spin relaxation times are predicted to be very long, making them promising for spintronics applications, whereas the possibility of hybrid devices based on the coupling between their spin and valley degrees of freedom opens unprecedented opportunities for innovative valleytronics. Given this, it is crucial to understand the fundamental limits on the spin lifetime of these materials.

A recent paper in Physical Review Letters makes a step towards solving a fundamental limiting source of spin lifetimes in perfectly clean systems in presence of Rashba spin-orbit interaction. While the study has focused on the case of graphene, the theoretical analysis is easily generalizable and applicable to any material with spin-split bands, including the two-dimensional electron gas and 2D materials, as well as the surface states of topological insulators.

This theoretical work was carried out by Aron W. Cummings, a researcher in the Theoretical and Computational Nanoscience Group of ICN2, headed by ICREA Research Prof. Stephan Roche.

Article reference:

Aron W. Cummings and Stephan Roche
Effects of Dephasing on Spin Lifetime in Ballistic Spin-Orbit Materials
Physical Review Letters 116, 086602 (2016)
http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.086602