Additional Evidence for the Surface Origin of the Peculiar Angular-Dependent Magnetoresistance Oscillations Discovered in a Topological Insulator Bi_{1-x}Sb_{x}

We present detailed data on the unusual angular-dependent magnetoresistance oscillation phenomenon recently discovered in a topological insulator Bi_{0.91}Sb_{0.09}. Direct comparison of the data taken before and after etching the sample surface gives compelling evidence that this phenomenon is essentially originating from a surface state. The symmetry of the oscillations suggests that it probably comes from the (111) plane, and obviously a new mechanism, such as a coupling between the surface and the bulk states, is responsible for this intriguing phenomenon in topological insulators.Comment: 5 pages, 4 figures, Proceedings manuscript for the 19th International Conference on the Application of High Magnetic Fields in Semiconductor Physics and Nanotechnology (HMF-19

Ising-like Spin Anisotropy and Competing Antiferromagnetic - Ferromagnetic Orders in GdBaCo_{2}O_{5.5} Single Crystals

In RBaCo_{2}O_{5+x} compounds (R is rare earth), a ferromagnetic-antiferromagnetic competition is accompanied by a giant magnetoresistance. We study the magnetization of detwinned GdBaCo_{2}O_{5.5} single crystals, and find a remarkable uniaxial anisotropy of Co^{3+} spins which is tightly linked with the chain oxygen ordering in GdO_{0.5} planes. Reflecting the underlying oxygen order, CoO_2 planes also develop a spin-state order consisting of Co^{3+} ions in alternating rows of S=1 and S=0 states. The magnetic structure appears to be composed of weakly coupled ferromagnetic ladders with Ising-like moments, which gives a simple picture for magnetotransport phenomena.Comment: 5 pages, 4 figures, accepted to Phys.Rev.Let

Management and Organization in the work of Michel Houellebecq

Research in management and organization may only gain by being inspired from arts, culture and humanities in order to rethink practices but also to nourish its own perspectives. Life in organizations is artificially separate from ordinary life: all of mundane objects are thus conducive to astonishment, inspiration, and even problematization. The unplugged subsection “voices” gives the opportunity to academics and non-academics to deliver an interpretation about an object from the cultural or artistic world. Interpreted objects are or not directly related to organizational life, resonate or not with the moment, but share some intriguing features. These interpretations suggest a patchwork of variations on the same object

Development of a Taxonomy to be used by Business-IT Alignment Researchers

The nexus between Business and IT research is complex. Due to extended research over time, the context of business-IT alignment has resulted in many different conceptualisations that can be applied to ongoing research. It is challenging to select and adopt a suitable approach to study business-IT alignment across any given field due to the variability of the existing conceptualisations. This study reviews the existing literature to identify alignment conceptualisations and contributes to both theory and practice. Theoretically, through the uncovering of gaps in the literature a taxonomy has been developed which can be used as a guide to select an appropriate alignment lens for business-IT alignment studies. In practice, it is expected that this taxonomy will be beneficial for conceptualising the structure and philosophies underpinning future alignment studies. To validate the taxonomy, the paper presents a case study in healthcare applying the developed taxonomy to investigate alignment of big data in health

Break-up of nano-particle agglomerates by hydrodynamically limited processes

When dry nano-particulate powders are first added into a liquid, clusters as large as hundreds of microns can be formed. In this study, high shear impellers, such as the sawtooth Ekatomizer and rotor-stator impellers were used to suspend and break-up these agglomerates in a stirred vessel. The high local energy dissipation rates generated by these impeller could slowly break up clusters to sub-micron sizes by an erosional mechanism. In comparison, single and multiple passes through a valve homogeniser could quickly break the nano-particle clusters to sub-micron sizes; single pass operation had the highest breakage efficiency for a given specific energy input. For both equipment types, the rate of fines generation was found to be controlled by the maximum energy dissipation rate. However, the size of the fine aggregates produced was a constant and was not a function of the energy dissipation rate

E(2)-Equivariant Graph Planning for Navigation

Learning for robot navigation presents a critical and challenging task. The scarcity and costliness of real-world datasets necessitate efficient learning approaches. In this letter, we exploit Euclidean symmetry in planning for 2D navigation, which originates from Euclidean transformations between reference frames and enables parameter sharing. To address the challenges of unstructured environments, we formulate the navigation problem as planning on a geometric graph and develop an equivariant message passing network to perform value iteration. Furthermore, to handle multi-camera input, we propose a learnable equivariant layer to lift features to a desired space. We conduct comprehensive evaluations across five diverse tasks encompassing structured and unstructured environments, along with maps of known and unknown, given point goals or semantic goals. Our experiments confirm the substantial benefits on training efficiency, stability, and generalization

Observations of two-dimensional quantum oscillations and ambipolar transport in the topological insulator Bi2Se3 achieved by Cd doping

We present a defect-engineering strategy to optimize the transport properties of the topological insulator Bi2Se3 to show a high bulk resistivity and clear quantum oscillations. Starting with a p-type Bi2Se3 obtained by combining Cd doping and a Se-rich crystal-growth condition, we were able to observe a p-to-n-type conversion upon gradually increasing the Se vacancies by post annealing. With the optimal annealing condition where a high level of compensation is achieved, the resistivity exceeds 0.5 Ohmcm at 1.8 K and we observed two-dimensional Shubnikov-de Haas oscillations composed of multiple frequencies in magnetic fields below 14 T.Comment: 7 pages, 6 figure

Band structure engineering in (Bi1-xSbx)2Te3 ternary topological insulators

Three-dimensional (3D) topological insulators (TI) are novel quantum materials with insulating bulk and topologically protected metallic surfaces with Dirac-like band structure. The spin-helical Dirac surface states are expected to host exotic topological quantum effects and find applications in spintronics and quantum computation. The experimental realization of these ideas requires fabrication of versatile devices based on bulk-insulating TIs with tunable surface states. The main challenge facing the current TI materials exemplified by Bi2Se3 and Bi2Te3 is the significant bulk conduction, which remains unsolved despite extensive efforts involving nanostructuring, chemical doping and electrical gating. Here we report a novel approach for engineering the band structure of TIs by molecular beam epitaxy (MBE) growth of (Bi1-xSbx)2Te3 ternary compounds. Angle-resolved photoemission spectroscopy (ARPES) and transport measurements show that the topological surface states exist over the entire composition range of (Bi1-xSbx)2Te3 (x = 0 to 1), indicating the robustness of bulk Z2 topology. Most remarkably, the systematic band engineering leads to ideal TIs with truly insulating bulk and tunable surface state across the Dirac point that behave like one quarter of graphene. This work demonstrates a new route to achieving intrinsic quantum transport of the topological surface states and designing conceptually new TI devices with well-established semiconductor technology.Comment: Minor changes in title, text and figures. Supplementary information adde

Ultra-low carrier concentration and surface dominant transport in Sb-doped Bi2Se3 topological insulator nanoribbons

A topological insulator is a new state of matter, possessing gapless spin-locking surface states across the bulk band gap which has created new opportunities from novel electronics to energy conversion. However, the large concentration of bulk residual carriers has been a major challenge for revealing the property of the topological surface state via electron transport measurement. Here we report surface state dominated transport in Sb-doped Bi2Se3 nanoribbons with very low bulk electron concentrations. In the nanoribbons with sub-10nm thickness protected by a ZnO layer, we demonstrate complete control of their top and bottom surfaces near the Dirac point, achieving the lowest carrier concentration of 2x10^11/cm2 reported in three-dimensional (3D) topological insulators. The Sb-doped Bi2Se3 nanostructures provide an attractive materials platform to study fundamental physics in topological insulators, as well as future applications.Comment: 5 pages, 4 figures, 1 tabl