1,478 research outputs found
Observation of plateau-like magnetoresistance in twisted Fe3GeTe2/Fe3GeTe2 junction
No full text© 2020 Author(s). Controlling the stacking of van der Waals (vdW) materials is found to produce exciting new findings, since hetero- or homo-structures have added the diverse possibility of assembly and manipulated functionalities. However, so far, the homostructure with a twisted angle based on the magnetic vdW materials remains unexplored. Here, we achieved a twisted magnetic vdW Fe3GeTe2 (FGT)/Fe3GeTe2 junction with broken crystalline symmetry. A clean and metallic vdW junction is evidenced by the temperature-dependent resistance and the linear I-V curve. Unlike the pristine FGT, a plateau-like magnetoresistance (PMR) is observed in the magnetotransport of our homojunction due to the antiparallel magnetic configurations of the two FGT layers. The PMR ratio is found to be similar to 0.05% and gets monotonically enhanced as temperature decreases like a metallic giant magnetoresistance. Such a tiny PMR ratio is at least three orders of magnitude smaller than the tunneling magnetoresistance ratio, justifying our clean metallic junction without a spacer. Our findings demonstrate the feasibility of the controllable homostructure and shed light on future spintronics using magnetic vdW materials. Published under license by AIP Publishing11sciescopu
Exciton-driven antiferromagnetic metal in a correlated van der Waals insulator
No full text© 2021, The Author(s).Collective excitations of bound electron-hole pairs—known as excitons—are ubiquitous in condensed matter, emerging in systems as diverse as band semiconductors, molecular crystals, and proteins. Recently, their existence in strongly correlated electron materials has attracted increasing interest due to the excitons’ unique coupling to spin and orbital degrees of freedom. The non-equilibrium driving of such dressed quasiparticles offers a promising platform for realizing unconventional many-body phenomena and phases beyond thermodynamic equilibrium. Here, we achieve this in the van der Waals correlated insulator NiPS3 by photoexciting its newly discovered spin–orbit-entangled excitons that arise from Zhang-Rice states. By monitoring the time evolution of the terahertz conductivity, we observe the coexistence of itinerant carriers produced by exciton dissociation and a long-wavelength antiferromagnetic magnon that coherently precesses in time. These results demonstrate the emergence of a transient metallic state that preserves long-range antiferromagnetism, a phase that cannot be reached by simply tuning the temperature. More broadly, our findings open an avenue toward the exciton-mediated optical manipulation of magnetism.11Nsciescopu
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Retraction: Crystal structure of a Baeyer–Villiger flavin‐containing monooxygenase from Staphylococcus aureus MRSA strain MU50, William C. Hwang, Qingping Xu, Bainan Wu, Adam Godzik
No full textThe above article from Proteins: Structure, Function, and Bioinformatics, published online on 5 August 2014 in Wiley Online Library (http://onlinelibrary.wiley.com/doi/10.1002/prot.24661/full), has been retracted by agreement between William C. Hwang, Qingping Xu, Bainan Wu, Adam Godzik, the Editor‐in‐Chief, Bertrand E. Garcia‐Moreno, and Wiley Periodicals, Inc. The retraction has been agreed because submission was made without agreement from co‐author Adam Godzik
Author Correction: Understanding the role of bitter taste perception in coffee, tea and alcohol consumption through Mendelian randomization
No full textAn amendment to this paper has been published and can be accessed via a link at the top of the paper. The original version of this Article contained an error in the author name Liang-Dar Hwang, which was incorrectly given as Daniel Liang-Dar Hwang
Tuning dimensionality in van-der-Waals antiferromagnetic Mott insulators <i>TM</i>PS<sub>3</sub>
No full textWe present an overview of our recent work in tuning and controlling the structural, magnetic and electronic dimensionality of 2D van-der-Waals antiferromagnetic compounds (Transition-Metal)PS3. Low-dimensional magnetic systems such as these provide rich opportunities for studying new physics and the evolution of established behaviours with changing dimensionality. These materials can be exfoliated to monolayer thickness and easily stacked and combined into functional heterostructures. Alternatively, the application of hydrostatic pressure can be used to controllably close the van-der-Waals interplanar gap and tune the crystal structure and electron exchange paths towards a 3D nature. We collect and discuss trends and contrasts in our data from electrical transport, Raman scattering and synchrotron x-ray measurements, as well as insight from theoretical calculations and other results from the literature. We discuss structural transitions with pressure common to all materials measured, and link these to Mott insulator-transitions in these compounds at high pressures. Key new results include magnetotransport and resistivity data in the high-pressure metallic states, which show potentially interesting qualities for a new direction of future work focused on low temperature transport and quantum critical physics
Cone structures and parabolic geometries
No full text© 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.A cone structure on a complex manifold M is a closed submanifold C⊂ PTM of the projectivized tangent bundle which is submersive over M. A conic connection on C specifies a distinguished family of curves on M in the directions specified by C. There are two common sources of cone structures and conic connections, one in differential geometry and another in algebraic geometry. In differential geometry, we have cone structures induced by the geometric structures underlying holomorphic parabolic geometries, a classical example of which is the null cone bundle of a holomorphic conformal structure. In algebraic geometry, we have the cone structures consisting of varieties of minimal rational tangents (VMRT) given by minimal rational curves on uniruled projective manifolds. The local invariants of the cone structures in parabolic geometries are given by the curvature of the parabolic geometries, the nature of which depend on the type of the parabolic geometry, i.e., the type of the fibers of C→ M. For the VMRT-structures, more intrinsic invariants of the conic connections which do not depend on the type of the fiber play important roles. We study the relation between these two different aspects for the cone structures induced by parabolic geometries associated with a long simple root of a complex simple Lie algebra. As an application, we obtain a local differential-geometric version of the global algebraic-geometric recognition theorem due to Mok and Hong–Hwang. In our local version, the role of rational curves is completely replaced by appropriate torsion conditions on the conic connection.11Nsciescopu
A 'Composite' Stepped Plate for Use in Highly Directional Parametric Array Loudspeakers
No full textIt has been shown that stepped plate radiators with appropriately designed steps can be used in highly directional parametric array (PA) loudspeakers [Hwang and Moon, 170th Meeting of the Acoustical Society of America, 138(3), 1801(2015)]. To improve the performance of the PA loudspeaker, a relatively thin plate with steps needs to be adopted for its higher power efficiency. However, the natural frequencies of the plate and the corresponding mode shapes depend on the mass of the steps. Hence, it can be difficult to design a stepped plate suitable for use in PA loudspeakers. In this paper, we propose a novel plate design, with steps composed of a stiff, lightweight, polymer material. The steps were fabricated with a thickness of 2.3 mm from a polymer material with an elastic modulus of 1 GPa, a Poisson ratio of 0.23, and a mass density of 540 kg/m3 on the plate with a thickness of 1 mm. Experiments and simulations were carried out to determine the acoustic characteristics of our fabricated “composite” stepped plate. [Work supported by NRF 2016R1E1A2A02945515).]
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Retraction: Site‐specific recombination of nitrogen‐fixation genes in cyanobacteria by XisF–XisH–XisI complex: Structures and models, William C. Hwang, James W. Golden, Jaime Pascual, Dong Xu, Anton Cheltsov, Adam Godzik
No full textThe above article from the Proteins: Structure, Function, and Bioinformatics, published online on 1 September 2014 in Wiley Online Library as Accepted Article (http://onlinelibrary.wiley.com/doi/10.1002/prot.24679/full), has been retracted by agreement between William C. Hwang, James W. Golden, Jaime Pascual, Dong Xu, Anton Cheltsov, Adam Godzik, the Editor‐in‐Chief, Bertrand E. Garcia‐Moreno, and Wiley Periodicals, Inc. The retraction has been agreed because submission was made without agreement from co‐author Adam Godzik
Research in Accounting for Income Taxes
No full textThis paper comprehensively reviews Accounting for Income Taxes (AFIT). The first half provides background and a primer on AFIT. The second half reviews existing studies in detail and offers suggestions for future research. We emphasize the research questions that have been addressed (most of which relate to whether the tax accounts are used to manage earnings, and whether the tax accounts are priced by equity market participants) and highlight areas that have not received much research attention. We close with a call for a theoretical framework, more study of the inconsistencies between research and practice, and improved econometrics.
Scientific ermeneutics and Fiction_____ a study of Hwang-Hai and his science fiction
No full textAfter developing for a century, science fictions and movies are becoming huge culture enterprises in Europe and America. But in Taiwan, the audiences and readers are only interested in special effect Hollywood movies or comics, science fictions are still considered deduction novels and being put aside. Writers don\ue2t want to invest their time to initiate a science fiction, but Hwang-Hai does.
Hwang-Hai had TB since he was young. He dropped out from school at grade 8 to fight the disease. Beyond his sickness, he kept learning and practicing writing, and making a profit from payment of written to improve his family finance. He started his science fiction writing when he was 26 years old, and kept on writing until now, for 40 years. His creation list is just like an epitome of Taiwan science fiction literature history. He was an ascetic monk of science fiction writing, walking haltingly, alone on his way, kept standing on and became evergreen of science literature among Taiwan writers.
TB like the shadow following Hwang-Hai during his adolescent, but he kept on learning and writing. At age 31, he passed high school educational authenticate exam and joint college entrance examination, accomplished his dream on college study. After age 40, he won a lot award on literature and his achievement is approved by literary circles.
Hwang-Hai\ue2s writing includes literary novels, prose, columns, science articles, and adult and children science fictions. The author wants to build up the interaction between science evolutions and the developing history of science fictions by historical analysis, and tries to establish the relationship among scientific hermeneutics, sociology, arts, psychology and philology by theoretical research, and studies the details of his creations one by one on literature text, to posit his role in science literature history of Taiwan.
Keywords: Science fiction, Hwang-Hai, Robot, UFO, time machine, Scientific Hermeneutics
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