arXiv subjects

Gabriel R. Schleder

Publications and source records attributed to Gabriel R. Schleder.

23 records · Page 2Linked to original sources

arXiv2020

Structural and electronic properties of realistic two-dimensional amorphous topological insulators

We investigate the structure and electronic spectra properties of two-dimensional amorphous bismuthene structures and show that these systems are topological insulators. We employ realistic modeling of amorphous geometries together with density functional theory for electronic structure calculations. We investigate the system topological properties throughout the amorphization process and find that the robustness of the topological phase is associated with the spin-orbit coupling strength and size of the pristine topological gap. Using recursive non-equilibrium Green's function, we study the electronic transport properties of nanoribbons devices with lengths comparable to experimentally synthesized materials. We find a $2e^2/h$ conductance plateau within the topological gap and an onset of Anderson localization at the trivial insulator phase.

cond-mat.mtrl-sci↗

arXiv2020

Dual Topological Insulator Device with Disorder Robustness

Two-dimensional Na$_3$Bi is a dual topological insulator protected by time-reversal and mirror symmetry, resulting in a promising platform for devices design. However, in reality, the design of topological devices is hindered by a sensitivity against disorder and temperature. We study the topological properties of Na$_3$Bi in the presence of intrinsic defects, investigating the robustness of the edge states and the resulting transport properties. We apply a recursive Green's function technique enabling the study of disordered systems with lengths comparable to experimentally synthesized materials, in the order of micrometers. We combine our findings to propose a topological insulator device, where intrinsic defects are used to filter the response of trivial bulk states. This results in a stable conductance throughout a large range of electronic temperatures, and controllable by a perpendicular electric field. Our proposal is general, enabling the design of various dual topological insulators devices.

cond-mat.mes-hall↗

arXiv2020

Discovery of Higher-Order Topological Insulators using the Spin Hall Conductivity as a Topology Signature

The discovery and realization of topological insulators, a phase of matter which hosts metallic boundary states when the $d$-dimension insulating bulk is confined to ($d-1$)-dimensions, led to several potential applications. Recently, it was shown that protected topological states can manifest in ($d-2$)-dimensions, such as hinge and corner states for three- and two-dimensional systems, respectively. These nontrivial materials are named higher-order topological insulators (HOTIs). Here we show a connection between spin Hall effect and HOTIs using a combination of {\it ab initio} calculations and tight-binding modeling. The model demonstrates how a non-zero bulk midgap spin Hall conductivity (SHC) emerges within the HOTI phase. Following this, we performed high-throughput density functional theory calculations to find unknown HOTIs, using the SHC as a criterion. We calculated the SHC of 693 insulators resulting in seven stable two-dimensional HOTIs. Our work guides novel experimental and theoretical advances towards higher-order topological insulators realization and applications.

cond-mat.mtrl-sci↗

arXiv2020

Tuning Hydrogen Adsorption and Electronic Properties from Graphene to Fluorographone

Graphene functionalization by hydrogen and fluorine has been proposed as a route to modulate its reactivity and electronic properties. However, until now, proposed systems present degradation and limited hydrogen adsorption capacity. In this study, combining first-principles calculations based on density functional theory (DFT) and reactive molecular dynamics, we analyze the tuning of hydrogen adsorption and electronic properties in fluorinated and hydrogenated monolayer graphenes. Our results indicate that fluorine adsorption promotes stronger carbon$-$hydrogen bonds. By changing the concentration of fluorine and hydrogen, charge density transfer and electronic properties such as the band gap and spin-splitting can be tailored, increasing their potential applicability for electronic and spintronic devices. Despite fluorine not affecting the total H incorporation, the $\textit{ab initio}$ molecular dynamics results suggest that 3% fluorinated graphene increases hydrogen anchoring, indicating the hydrogenated and fluorinated graphenes potential for hydrogen storage and related applications.

cond-mat.mtrl-sci↗

arXiv2019

Toward Realistic Amorphous Topological Insulators

The topological properties of materials are, until now, associated with the features of their crystalline structure, although translational symmetry is not an explicit requirement of the topological phases. Recent studies of hopping models on random lattices have demonstrated that amorphous model systems show a nontrivial topology. Using {\it ab initio} calculations we show that two-dimensional amorphous materials can also display topological insulator properties. More specifically, we present a realistic state-of-the-art study of the electronic and transport properties of amorphous bismuthene systems, showing that these materials are topological insulators. These systems are characterized by the topological index $\mathbb{Z}_{2}=1$ and bulk-edge duality, and their linear conductance is quantized, ${\cal G}=2e^{2}/h$, for Fermi energies within the topological gap. Our study opens the path to the experimental and theoretical investigation of amorphous topological insulator materials.

cond-mat.mtrl-sci↗