Abstract
A large and ideal Rashba-type spin-orbit splitting is desired for the applications of materials in spintronic devices and the detection of Majorana fermions in solids. Here, we propose an approach to achieve giant and ideal spin-orbit splittings through a combination of ordered surface alloying and interface engineering, that is, growing alloy monolayers on an insulating polar surface. We illustrate this unique strategy by means of first-principle calculations of buckled hexagonal monolayers of SbBi and PbBi supported on Al2O3(0001). Both systems display ideal Rashba-type states with giant spin-orbit splittings, characterized with energy offsets over 600 meV and momentum offsets over 0.3 Å−1, respectively. Our study thus points to an effective way of tuning spin-orbit splitting in low-dimensional materials to draw immediate experimental interest.
Highlights
The Rashba effect is referred to as the spin-orbit (SO) splitting at surfaces/interfaces due to the broken inversion symmetry [1,2], which has led to many exotic quantum phenomena and novel applications, ranging from the spin Hall effect, Majorana fermions in solids and the spin field-effect transistor [3,4,5]
The effective Rashba Hamiltonian for an electron with momentum k and spin σ can be written as HR = λσ · (Ez × k), where λ is the strength of the SO coupling (SOC) and Ez is the electric field perpendicular to the surface/interface created by a perpendicular potential gradient related to the structural asymmetry
Using density-functional theory (DFT) calculations, we show unprecedented large Rashba energy offsets over 600 meV and momentum offsets over 0.3 A −1 for both SbBi/Al2O3(0001) and PbBi/Al2O3(0001), which are roughly three times of those in Bi/Ag(111)
Summary
The Rashba effect is referred to as the spin-orbit (SO) splitting at surfaces/interfaces due to the broken inversion symmetry [1,2], which has led to many exotic quantum phenomena and novel applications, ranging from the spin Hall effect, Majorana fermions in solids and the spin field-effect transistor [3,4,5]. The effective Rashba Hamiltonian for an electron with momentum k and spin σ can be written as HR = λσ · (Ez × k), where λ is the strength of the SO coupling (SOC) and Ez is the electric field perpendicular to the surface/interface created by a perpendicular potential gradient related to the structural asymmetry. The Rashba SO splitting can be controlled by the electric polarization in ferroelectric materials and substrates [23,24,25,30,31,32]. Despite these achievements, natural materials exhibiting both giant and ideal Rashba states are rare. Artificial interfaces by a priori theoretical design are highly desirable to fill this outstanding gap
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