Spin Hall effect and Weak Antilocalization in Graphene/Transition Metal Dichalcogenide Heterostructures

We report on a theoretical study of the spin Hall Effect (SHE) and weak antilocal-ization (WAL) in graphene/transition metal dichalcogenide (TMDC) heterostructures, computed through efficient real-space quantum transport methods, and using realistic tight-binding models parametrized from ab initio calculations. The graphene/WS 2 system is found to maximize spin proximity effects compared to graphene on MoS 2 , WSe 2 , or MoSe 2 , with a crucial role played by disorder, given the disappearance of SHE signals in the presence of strong intervalley scattering. Notably, we found that stronger WAL effects are concomitant with weaker charge-to-spin conversion efficiency. For further experimental studies of graphene/TMDC heterostructures, our findings provide guidelines for reaching the upper limit of spin current formation and for fully harvesting the potential of two-dimensional materials for spintronic applications.Comment: This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in Nano Letters, copyright\c{opyright}American Chemical Society after peer review. To access the final edited and published work see http://pubs.acs.org/articlesonrequest/AOR-c2pZ8WnmG7pcF4MIivj

From classroom tutor to hypertext adviser: An evaluation

This paper describes a three‐year experiment to investigate the possibility of making economies by replacing practical laboratory sessions with courseware while attempting to ensure that the quality of the student learning experience did not suffer. Pathology labs are a central component of the first‐year medical undergraduate curriculum at Southampton. Activities in these labs had been carefully designed and they were supervised by lab demonstrators who were subject domain experts. The labs were successful in the eyes of both staff and students but were expensive to conduct, in terms of equipment and staffing. Year by year evaluation of the introduction of courseware revealed that there was no measurable difference in student performance as a result of introducing the courseware, but that students were unhappy about the loss of interaction with the demonstrators. The final outcome of this experiment was a courseware replacement for six labs which included a software online hypertext adviser. The contribution of this work is that it adds to the body of empirical evidence in support of the importance of maintaining dialogue with students when introducing courseware, and it presents an example of how this interaction might be achieved in software

Xenophon and the Nazis: A case study in the politicization of Greek thought through educational propaganda

In National Socialist Germany, radical reinterpretations of Classical texts were always on the agenda. The Reich Education Ministry decreed unequivocally that only those ancient texts which could serve the regime’s new ‘national-political’ education should be taught in schools, and many school-teachers were all too eager to follow this prime directive. This article will consider a number of articles on Xenophon published in the Nazi Teachers’ League (NSLB) Classics journal, Die Alten Sprachen, in order to illuminate the ways in which aspects of Xenophon’s thought could become ‘politicized’. Thus, one article takes selected passages from Xenophon’s Hellenica and weaves them into a treatise on ancient and modern political theory, condemning individualism and providing a systematic indictment of the dangers of democracy, while another elevates aspects of the Spartan constitution to the status of contemporary political principles, placing Sparta (rather than Athens) at the centre of the German political imagination. As a whole, the article seeks to reveal the contingency of political analysis based on the ancient world, and the ways in which, in certain circumstances, almost any aspect of Greek thought can become ‘political’. An authoritarian regime can just as easily style itself as an heir to the legacy of ancient politics as a democratic one, and Greek thought can ultimately be mobilized for almost any ends — however attractive or rebarbative these might seem to observers in today’s society.This is the author accepted manuscript. The final version is available from Oxford University Press via http://dx.doi.org/10.1093/crj/clv01

Spin transport in graphene/transition metal dichalcogenide heterostructures

Since its discovery, graphene has been a promising material for spintronics: its low spin-orbit coupling, negligible hyperfine interaction, and high electron mobility are obvious advantages for transporting spin information over long distances. However, such outstanding transport properties also limit the capability to engineer active spintronics, where strong spin-orbit coupling is crucial for creating and manipulating spin currents. To this end, transition metal dichalcogenides, which have larger spin-orbit coupling and good interface matching, appear to be highly complementary materials for enhancing the spin-dependent features of graphene while maintaining its superior charge transport properties. In this review, we present the theoretical framework and the experiments performed to detect and characterize the spin-orbit coupling and spin currents in graphene/transition metal dichalcogenide heterostructures. Specifically, we will concentrate on recent measurements of Hanle precession, weak antilocalization and the spin Hall effect, and provide a comprehensive theoretical description of the interconnection between these phenomena.Comment: 21 pages, 11 figures. This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in Nano Letters, copyright\c{opyright}American Chemical Society after peer review. To access the final edited and published work see http://pubs.rsc.org/en/Content/ArticleLanding/2018/CS/C7CS00864

Very low shot noise in carbon nanotubes

We have performed noise measurements on suspended ropes of single wall carbon nanotubes (SWNT) between 1 and 300 K for different values of dc current through the ropes. We find that the shot noise is suppressed by more than a factor 100 compared to the full shot noise 2eI. We have also measured an individual SWNT and found a level of noise which is smaller than the minimum expected. Another finding is the very low level of 1/f noise, which is significantly lower than previous observations. We propose two possible interpretations for this strong shot noise reduction: i) Transport within a rope takes place through a few nearly ballistic tubes within a rope and possibly involves non integer effective charges. ii) A substantial fraction of the tubes conduct with a strong reduction of effective charge (by more than a factor 50).Comment: Submitted to Eur. Phys. J. B (Jan. 2002) Higher resolution pictures are posted on http://www.lps.u-psud.fr/Collectif/gr_07/publications.htm

Effects of magnetic field and disorder on electronic properties of Carbon Nanotubes

Electronic properties of metallic and semiconducting carbon nanotubes are investigated in presence of magnetic field perpendicular to the CN-axis, and disorder introduced through energy site randomness. The magnetic field field is shown to induce a metal-insulator transition (MIT) in absence of disorder, and surprisingly disorder does not affect significantly the MIT. These results may find confirmation through tunneling experimentsComment: 4 pages, 6 figures. Phys. Rev. B (in press

Magnetic Insulator-Induced Proximity Effects in Graphene: Spin Filtering and Exchange Splitting Gaps

We report on first-principles calculations of spin-dependent properties in graphene induced by its interaction with a nearby magnetic insulator (Europium oxide, EuO). The magnetic proximity effect results in spin polarization of graphene $\pi$ orbitals by up to 24 %, together with large exchange splitting bandgap of about 36 meV. The position of the Dirac cone is further shown to depend strongly on the graphene-EuO interlayer. These findings point towards the possible engineering of spin gating by proximity effect at relatively high temperature, which stands as a hallmark for future all-spin information processing technologies.Comment: 5 pages, 4 figure

An improved sum-product estimate for general finite fields

This paper improves on a sum-product estimate obtained by Katz and Shen for subsets of a finite field whose order is not prime