arXiv subjects

L. B. Abdalla

Publications and source records attributed to L. B. Abdalla.

3 recordsLinked to original sources

arXiv2018

Unconventional spin texture in a non-centrosymmetric quantum spin Hall insulator

We proposed that the simultaneous presence of both Rashba and band inversion can lead to a Rashba-like spin-splitting formed by two bands with the same in-plane helical spin texture. Because of this unconventional spin texture, the backscattering is forbidden in edge and bulk conductivity channels. We propose a new non-centrosymmetric honeycomb-lattice quantum spin Hall (QSH) insulator family formed by the IV, V, and VII elements with this property. The system formed by Bi, Pb and I atoms is mechanically stable and has both a large Rashba spin-splitting of 60 meV and a large nontrivial band gap of 0.14 eV. Since the edge and the bulk states are protected by the TR symmetry, contrary to what happens in most doped QSH insulators, the bulk states do not contribute to the backscattering in the electronic transport, allowing the construction of a spintronic device with less energy loss.

cond-mat.mtrl-sci↗

arXiv2016

Transforming common III-V and II-VI semiconductor compounds into topological heterostructures: The case of CdTe/InSb superlattices

Currently known topological insulators (TIs) are limited to narrow gap compounds incorporating heavy elements, thus severely limiting the material pool available for such applications. We show via first-principle calculations how a heterovalent superlattice made of common semiconductor building blocks can transform its non-TI components into a topological nanostructure, illustrated by III-V/II-VI superlattice InSb/CdTe. The heterovalent nature of such interfaces sets up, in the absence of interfacial atomic exchange, a natural internal electric field that along with the quantum confinement leads to band inversion, transforming these semiconductors into a topological phase while also forming a giant Rashba spin splitting. We reveal the relationship between the interfacial stability and the topological transition, finding a window of opportunity where both conditions can be optimized. Once a critical InSb layer thickness above ~ 1.5 nm is reached, both [111] and [100] superlattices have a relative energy of 5-14 meV/A2 higher than that of the atomically exchanged interface and an excitation gap up to ~150 meV, affording room-temperature quantum spin Hall effect in semiconductor superlattices. The understanding gained from this study could significantly broaden the current, rather restricted repertoire of functionalities available from individual compounds by creating next-generation super-structured functional materials.

cond-mat.mtrl-sci↗

arXiv2014

Electric Field Induced Topological Phase Transition in Two-Dimensional Few-layer Black Phosphorus

Phosphorene is a novel two-dimensional material that can be isolated through mechanical exfoliation from layered black phosphorus, but unlike graphene and silicene, monolayer phosphorene has a large band gap. It was thus unsuspected to exhibit band inversion and the ensuing topological insulator behavior. It has recently attracted interest because of its proposed application as field effect transistors. Using first-principles calculations with applied perpendicular electric field F we predict a continuous transition from the normal insulator to a topological insulator and eventually to a metal as a function of F. The continuous tuning of topological behavior with electric field would lead to spin-separated, gapless edge states, i.e., quantum spins Hall effect. This finding opens the possibility of converting normal insulating materials into topological ones via electric field, and making a multi-functional field effect topological transistor that could manipulate simultaneously both spins and charge carrier.

cond-mat.mtrl-sci↗