Bryan P. Doyle

Bio: Bryan P. Doyle is an academic researcher from University of Johannesburg. The author has contributed to research in topics: Diamond & X-ray photoelectron spectroscopy. The author has an hindex of 20, co-authored 102 publications receiving 1478 citations. Previous affiliations of Bryan P. Doyle include University of Paris-Sud & AREA Science Park.

The BEAR Beamline at Elettra

Abstract: The BEAR (Bending Magnet for Emission Absorption and Reflectivity) beamline is installed at the right exit of the 8.1 bending magnet at ELETTRA. The beamline — in operation since January 2003 — delivers linear and circularly polarized radiation in the 5 – 1600 eV energy range. The experimental station is composed of a UHV chamber for reflectivity, absorption, fluorescence and angle resolved photoemission measurements and a UHV chamber for in‐situ sample preparation.

High-Pressure Ground State of SmB 6 : Electronic Conduction and Long Range Magnetic Order

Abstract: High-pressure $^{149}\mathrm{Sm}$ nuclear forward scattering of synchrotron radiation and specific heat measurements have been performed on the intermediate valent Kondo insulator ${\mathrm{SmB}}_{6}$. The results show that at a critical pressure ${p}_{c}\ensuremath{\approx}6\text{ }\text{ }\mathrm{GPa}$, where the charge gap closes, a first order transition occurs to a magnetically ordered state, which shows typical features of trivalent samarium compounds. The similarity with SmS stresses the role of local correlations and gives important insight into the debate on the local or itinerant character of the f electrons in heavy fermion systems.

Pressure-induced magnetic order in golden SmS.

Abstract: High pressure $^{149}\mathrm{S}\mathrm{m}$ nuclear forward scattering experiments have been performed on the nonmagnetic semiconductor SmS We present the first clear evidence that the closure of the insulating gap at ${p}_{\mathrm{\ensuremath{\Delta}}}\ensuremath{\approx}2\text{ }\text{ }\mathrm{G}\mathrm{P}\mathrm{a}$ coincides with the appearance of magnetic order The pressure-induced magnetic phase transition has some first order character and suggests that the Sm ions are nearly trivalent at ${p}_{\mathrm{\ensuremath{\Delta}}}$ A ${\mathrm{\ensuremath{\Gamma}}}_{\mathrm{8}}$ quartet crystal field ground state with a value of $\ensuremath{\sim}05{\mathrm{\ensuremath{\mu}}}_{\mathrm{B}}$ for the samarium magnetic moment is inferred from our results Considerable magnetic short range order is observed above the ordering temperature inferred from macroscopic measurements

Balancing intermolecular and molecule-substrate interactions in supramolecular assemblies

Abstract: Self-assembly of functional supra-molecular nanostructures is among the most promising strategies for further development of organic electronics. However, a poor control of the interactions driving the assembling phenomena still hampers the tailored growth of designed structures. Here exploration of how non-covalent molecule-substrate interactions can be modified on a molecular level is described. For that, mixtures of DIP and F16CuPc, two molecules with donor and acceptor character, respectively are investigated. A detailed study of their structural and electronic properties is performed. In reference to the associated single-component layers, the growth of binary layers results in films with strongly enhanced intermolecular interactions and consequently reduced molecule-substrate interactions. This new insight into the interplay among the aforementioned interactions provides a novel strategy to balance the critical interactions in the assembly processes by the appropriate choice of molecular species in binary supra-molecular assemblies, and thereby control the self-assembly of functional organic nanostructures.

31p-S-4 Giant Magnetoresistance in Magnetic Manganese Oxide with Intrinsic Antiferromagnetic Spin Structure

Abstract: Giant and isotropic magnetoresistance as huge as −53% was observed in magnetic manganese oxide La0.72Ca0.25MnOz films with an intrinsic antiferromagnetic spin structure. We ascribe this magnetoresistance to spin‐dependent electron scattering due to spin canting of the manganese oxide.

Negative thermal expansion in functional materials: controllable thermal expansion by chemical modifications

Abstract: Negative thermal expansion (NTE) is an intriguing physical property of solids, which is a consequence of a complex interplay among the lattice, phonons, and electrons. Interestingly, a large number of NTE materials have been found in various types of functional materials. In the last two decades good progress has been achieved to discover new phenomena and mechanisms of NTE. In the present review article, NTE is reviewed in functional materials of ferroelectrics, magnetics, multiferroics, superconductors, temperature-induced electron configuration change and so on. Zero thermal expansion (ZTE) of functional materials is emphasized due to the importance for practical applications. The NTE functional materials present a general physical picture to reveal a strong coupling role between physical properties and NTE. There is a general nature of NTE for both ferroelectrics and magnetics, in which NTE is determined by either ferroelectric order or magnetic one. In NTE functional materials, a multi-way to control thermal expansion can be established through the coupling roles of ferroelectricity-NTE, magnetism-NTE, change of electron configuration-NTE, open-framework-NTE, and so on. Chemical modification has been proved to be an effective method to control thermal expansion. Finally, challenges and questions are discussed for the development of NTE materials. There remains a challenge to discover a “perfect” NTE material for each specific application for chemists. The future studies on NTE functional materials will definitely promote the development of NTE materials.

Microstructural Characterization and Charge Transport in Thin Films of Conjugated Polymers

Abstract: The performance of semiconducting polymers has been steadily increasing in the last 20 years. Improved control over the microstructure of these materials and a deeper understanding of how the microstructure affects charge transport are partially responsible for such trend. The development and widespread use of techniques that allow to characterize the microstructure of semiconducting polymers is therefore instrumental for the advance of these materials. This article is a review of the characterization techniques that provide information used to enhance the understanding of structure/property relationships in semiconducting polymers. In particular, the applications of optical and X-ray spectroscopy, X-ray diffraction, and scanning probe techniques in this context are described.

Topological Kondo Insulators

Abstract: This article reviews recent theoretical and experimental work on a new class of topological material—topological Kondo insulators, which develop through the interplay of strong correlations and spin-orbit interactions. The history of Kondo insulators is reviewed along with the theoretical models used to describe these heavy fermion compounds. The Fu-Kane method of topological classification of insulators is used to show that hybridization between the conduction electrons and localized f electrons in these systems gives rise to interaction-induced topological insulating behavior. Finally, some recent experimental results are discussed, which appear to confirm the theoretical prediction of the topological insulating behavior in samarium hexaboride, where the long-standing puzzle of the residual low-temperature conductivity has been shown to originate from robust surface states.