Abstract
Computational researchers have identified a thin-film device with an order-of-magnitude improved control over current in spin transistors. Recent advances in two-dimensional materials have produced systems that can manipulate spin without magnetic fields, thanks to ‘Rashba effects’ that split interfacial spin bands. Using first-principles calculations and analytical modelling, Horng-Tay Jeng from National Tsing Hua University in Taiwan and co-workers now propose a new mechanism to produce giant Rashba splitting by exploiting the asymmetric properties of spin states at interfaces between a topological insulator and a thin metal. Their analysis revealed that two-dimensional surface states of topological insulators such as bismuth selenide interact significantly with quantum well states in nanometre-thin silver layers. The strong coupling induces a ‘giant’ Rashba splitting on silver layers, which could be used to produce nanoscale spin transistors operable at room temperature.
Highlights
One of the major tasks in the development of semiconductor spintronics is finding a material with remarkable Rashba-type splitting to control the spin current
The Dirac point of the surface state (SS) at the interface locates at approximately − 0.6 eV, whereas at the surface side the Dirac point locates at approximately − 0.4 eV
The induced strong energy separation in these spin-splitting Ag quantum well states (QWSs) is ~ 0.35 eV, which is large compared with the Rashba energy parameter, ER, of other reported systems listed in Supplementary Table S1
Summary
One of the major tasks in the development of semiconductor spintronics is finding a material with remarkable Rashba-type splitting to control the spin current. The Datta-Das spin transistor,[1] proposed for more than 20 years, switches the spin current by controlling the magnitude of Rashba splitting of a two-dimensional electron gas in a semiconductor heterostructure.[2,3,4,5,6] After decades of trials, the Datta-Das spin transistor has been experimentally realized recently.[7] the mild splitting of the two-dimensional electron gas bands is inapplicable for spin transistors working at room temperature or designed in the nanoscale.[7,8,9] A much more feasible approach is highly desirable. Regarding the influence of the metal host, the SS would be hidden in the spintronics functions; efforts have been made on searching for materials with remarkable Rashba splittings for bulk carriers such as BiTeI (refs 13–16)
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