Spin- and angle-resolved photoemission on topological materials

A historical review of spin- and angle-resolved photoemission on topological materials is presented, aimed at readers who are new to the field or who wish to obtain an overview of the activities in the field. The main focus lies on topological insulators, but also Weyl and other semimetals will be discussed. Further it will be explained why the measured spin polarisation from a spin polarised state should always add up to 100% and how spin interference effects influence the measured spin texture.Comment: Invited review article for special issue "ARPES Studies of Topological Materials" in Electronic Structur

Polynomials Related to Harmonic Numbers and Evaluation of Harmonic Number Series I

In this paper we focus on two new families of polynomials which are connected with exponential polynomials and geometric polynomials. We discuss their generalizations and show that these new families of polynomials and their generalizations are useful to obtain closed forms of some series related to harmonic numbers.Comment: 18 page

A Feasibility Study of RIP Using 2.4 GHz 802.15.4 Radios

This paper contains a feasibility study of Radio Interferometric Positioning (RIP) implemented on a widely used 2.4 GHz radio (CC2430). RIP is a relatively new localization technique that uses signal strength measurements. Although RIP outperforms other RSS-based localization techniques, it imposes a set of unique requirements on the used radios. Therefore, it is not surprising that all existing RIP implementations use the same radio (CC1000), which operates below the 1 GHz range. This paper analyzes to what extent the CC2430 complies with these requirements. This analysis shows that the CC2430 platform introduces large and dynamic sources of errors. Measurements with a CC2430 test bed in a line-of-sight indoor environment verify this. The measurements indicate that the existing RIP algorithm cannot cope with these types of errors, and will incur a relatively low accuracy of 3.1 meter. Based on these results, we made an initial implementation of a new algorithm, which can cope with these errors, and decreases this positioning error by a factor of two to 1.5 meter accuracy

Investigating Exponential and Geometric Polynomials with Euler-Seidel Algorithm

In this paper we use Euler-Seidel matrices method to find out some properties of exponential and geometric polynomials and numbers. Some known results are reproved and some new results are obtained.Comment: 12 page

Evaluation of a tool for Java structural specification checking

Although a number of tools for evaluating Java code functionality and style exist, little work has been done in a distance learning context on automated marking of Java programs with respect to structural specifications. Such automated checks support human markers in assessing students’ work and evaluating their own marking; online automated marking; students checking code before submitting it for marking; and question setters evaluating the completeness of questions set. This project developed and evaluated a prototype tool that performs an automated check of a Java program’s correctness with respect to a structural specification. Questionnaires and interviews were used to gather feedback on the usefulness of the tool as a marking aid to humans, and on its potential usefulness to students for self-assessment when working on their assignments. Markers were asked to compare the usefulness of structural specification testing as compared to other kinds of support, including syntax error assistance, style checking and functionality testing. Initial results suggest that most markers using the structural specification checking tool found it to be useful, and some reported that it increased their accuracy in marking. Reasons for not using the tool included lack of time and the simplicity of the assignment it was trialled on. Some reservations were expressed about reliance on tools for assessment, both for markers and for students. The need for advice on incorporating tools in marking workflow is suggested

Determination of the time scale of photoemission from the measurement of spin polarization

The Eisenbud-Wigner-Smith (EWS) time delay of photoemission depends on the phase term of the matrix element describing the transition. Because of an interference process between partial channels, the photoelectrons acquire a spin polarization which is also related to the phase term. The analytical model for estimating the time delay by measuring the spin polarization is reviewed in this manuscript. In particular, the distinction between scattering EWS and interfering EWS time delay will be introduced, providing an insight in the chronoscopy of photoemission. The method is applied to the recent experimental data for Cu(111) presented in M. Fanciulli et al., PRL 118, 067402 (2017), allowing to give better upper and lower bounds and estimates for the EWS time delays.Comment: 30 pages, 5 figure