625 research outputs found
A L\'evy flight for electrons in graphene: superdiffusive-to-diffusive transport transition
In this work we propose an electronic L\'evy flight device, analogous to a
recent optical realization. To that end, we investigate the transmission of
electrons in graphene nanoribbons in the presence of circular electrostatic
clusters, whose diameter follow a power-law distribution. We analyze the effect
of the electrostatic clusters on the electronic transport regime of the
nanoribbons, in terms of its diffusion behavior. Our numerical calculations
show that the presence of circular electrostatic clusters induces a transition
from L\'evy (superdiffusive) to diffusive transport as the energy increases.
Furthermore, we argue that in our electronic L\'evy flight device,
superdiffusive transport is an exclusive feature of the low-energy quantum
regime, while diffusive transport is a feature of the semiclassical regime.
Therefore, we attribute the observed transition to the chiral symmetry
breaking, once the energy moves away from the Dirac point of graphene.Comment: Accepted for publication as a Regular Article in Physical Review
Orbital Hall effect and topology on a two-dimensional triangular lattice: from bulk to edge
We investigate a generalized multi-orbital tight-binding model on a
triangular lattice, a system prevalent in a wide range of two-dimensional
materials, and particularly relevant for simulating transition metal
dichalcogenide monolayers. We show that the interplay between spin-orbit
coupling and different symmetry-breaking mechanisms leads to the emergence of
four distinct topological phases [Eck, P., \textit{et al.}, Phys. Rev. B, 107
(11), 115130 (2023)]. Remarkably, this interplay also triggers the orbital Hall
effect with distinguished characteristics. Furthermore, by employing the
Landauer-B\"uttiker formula, we establish that in the orbital Hall insulating
phase, the orbital angular momentum is carried by edge states present in
nanoribbons with specific terminations. We also show that, as expected, they do
not have topological protection against the disorder of the edge states
belonging to a first-order topological insulator
Effect of proximity-induced spin-orbit coupling in graphene mesoscopic billiards
van der Waals heterostructures based on two-dimensional materials have recently become a very active topic of research in spintronics, both aiming at a fundamental description of spin dephasing processes in nanostructures and as a potential element in spin-based information processing schemes. Here, we theoretically investigate the magnetoconductance of mesoscopic devices built from graphene proximity-coupled to a high spin-orbit coupling material. Through numerically exact tight-binding simulations, we show that the interfacial breaking of inversion symmetry generates robust weak antilocalization even when the z → −z symmetric spin-orbit coupling in the quantum dot dominates over the Bychkov-Rashba interaction. Our findings are interpreted in the light of random matrix theory, which links the observed behavior of quantum interference corrections to a transition from a circular-orthogonal to circular-symplectic ensemble
Phenotypic and genotypic monitoring of Schistosoma mansoni in Tanzanian schoolchildren five years into a preventative chemotherapy national control programme
We conducted combined in vitro PZQ efficacy testing with population genetic analyses of S. mansoni collected from children from two schools in 2010, five years after the introduction of a National Control Programme. Children at one school had received four annual PZQ treatments and the other school had received two mass treatments in total. We compared genetic differentiation, indices of genetic diversity, and estimated adult worm burden from parasites collected in 2010 with samples collected in 2005 (before the control programme began) and in 2006 (six months after the first PZQ treatment). Using 2010 larval samples, we also compared the genetic similarity of those with high and low in vitro sensitivity to PZQ
Distribuição espacial de Tenuipalpus heveae Baker (Acari: Tenuipalpidae) na cultura da seringueira
- …