检索结果-内蒙古大学图书馆

Theory of scanning gate microscopy imaging of the supercurrent distribution in a planar Josephson junction

学校读者我要写书评

暂无评论

Physical Review B 2022年第3期106卷 035432-035432页

作者： K. Kaperek S. Heun M. Carrega P. Wójcik M. P. Nowak AGH University of Science and Technology Faculty of Physics and Applied Computer Science al. A. Mickiewicza 30 30-059 Krakow Poland NEST Istituto Nanoscienze-CNR and Scuola Normale Superiore Piazza San Silvestro 12 56127 Pisa Italy CNR-SPIN Via Dodecaneso 33 16146 Genova Italy AGH University of Science and Technology Academic Centre for Materials and Nanotechnology al. A. Mickiewicza 30 30-059 Krakow Poland

We theoretically investigate the mapping of the supercurrent distribution in a planar superconductor-normal-superconductor junction in the presence of a perpendicular magnetic field via the scanning gate microscopy technique. We find that the distribution of counterpropagating supercurrents aligned in Josephson vortices can be mapped by the change in the critical current induced by the tip of the scanning probe if the flux in the junction is set close to the maxima of the Fraunhofer pattern. Instead, when the magnetic field drives the junction to a supercurrent minimum in the Fraunhofer pattern, the superconducting phase adapts, and the tip always increases the supercurrent. The perpendicular magnetic field leads to the formation of Josephson vortices, whose extension for highly transparent junctions depends on the current circulation direction. We show that this leads to an asymmetric supercurrent distribution in the junction and that this can be revealed by scanning gate microscopy. We explain our findings on the basis of numerical calculations for both short- and long-junction limits and provide a phenomenological model for the observed phenomena.

关键词： Critical current Quantum transport Vortex lattices Josephson junctions Scanning probe microscopy

Finding hardness reductions automatically using SAT solvers

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Bergold, Helena Scheucher, Manfred Schröder, Felix Department of Computer Science Freie Universität Berlin Germany Institut für Mathematik Technische Universität Berlin Germany Department of Applied Mathematics Faculty of Mathematics and Physics Charles University Prague Czech Republic

In this article, we show that the completion problem, i.e. the decision problem whether a partial structure can be completed to a full structure, is NP-complete for many combinatorial structures. While the gadgets for most reductions in literature are found by hand, we present an algorithm to construct gadgets in a fully automated way. Using our framework which is based on SAT, we present the first thorough study of the completion problem on sign mappings with forbidden substructures by classifying thousands of structures for which the completion problem is NP-complete. Our list in particular includes interior triple systems, which were introduced by Knuth towards an axiomatization of planar point configurations. Last but not least, we give an infinite family of structures generalizing interior triple system to higher dimensions for which the completion problem is NP-complete. Copyright © 2024, The Authors. All rights reserved.

关键词：

Imprinting of Antiferromagnetic Vortex States in NiO-Fe Nanostructures

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Ślęzak, M. Wagner, T. Bharadwaj, V.K. Gomonay, O. Koziol-Rachwal, A. Menteş, T.O. Locatelli, A. Zając, M. Wilgocka-Ślęzak, D. Dróżdż, P. Ślęzak, T. AGH University of Krakow Faculty of Physics and Applied Computer Science Kraków Poland Institute of Physics Johannes Gutenberg-University Mainz Mainz55099 Germany Elettra - Sincrotrone Trieste S.C.p.A. Basovizza Trieste Italy National Synchrotron Radiation Centre SOLARIS Jagiellonian University Kraków Poland Jerzy Haber Institute of Catalysis and Surface Chemistry PAS Kraków Poland Institute of Physics Maria Curie-Sklodowska University Lublin Poland

Magnetic vortices are topological spin structures frequently found in ferromagnets, yet novel to antiferromagnets. By combining experiment and theory, we demonstrate that in a nanostructured antiferromagnetic-ferromagnetic NiO(111)-Fe(110) bilayer, a magnetic vortex is naturally stabilized by magnetostatic interactions in the ferromagnet and is imprinted onto the adjacent antiferromagnet via interface exchange coupling. We use micromagnetic simulations to construct a corresponding phase diagram of the stability of the imprinted antiferromagnetic vortex state. Our in depth analysis reveals that the interplay between interface exchange coupling and the antiferromagnet magnetic anisotropy plays a crucial role in locally reorienting the Néel vector out-of-plane in the prototypical in-plane antiferromagnet NiO and thereby stabilizing the vortices in the antiferromagnet. © 2024, CC BY.

关键词： Nickel oxide

Antiferromagnetic domains distribution carried by stoichiometry

学校读者我要写书评

暂无评论

Antiferromagnetic domains distribution carried by stoichiome...

2023 IEEE International Magnetic Conference - Short Papers, INTERMAG Short Papers 2023

作者： Mandziak, Anna De La Figuera, Juan Emilio Prieto, Jose Quesada, Adrian Miralles, Cecilia Granados Berja, Alba Aballe, Lucia Foerster, Michael Nino, Miguel Angel Nita, Pawel Solaris Synchrotron Czerwone Maki 98 Cracow30-392 Poland MadridE-28006 Spain MadridE-28049 Spain Alba Synchrotron Light Facility Cells BarcelonaE-08290 Spain Jagiellonian University Faculty of Physics Astronomy and Applied Computer Science ul. prof. Stanislawa Lojasiewicza 11 Cracow30-348 Poland

ISBN: (纸本)9798350338362

We present a spatially resolved X-ray magnetic linear dichroism study of high quality micron-sized mixed nickel-cobalt oxide (NCO) crystals. NixCo1-xO were prepared in-situ by high-temperature oxygen-assisted molecular beam epitaxy on Ru(0001) single crystal. To check the effect of incorporating Ni in the cobalt oxide films, three different composition were prepared. The element specific XMLD measurements reveal strong antiferromagnetic contrast at room temperature and magnetic domains up to one micron wide, reflecting the high structural quality of the islands. By means of vectorial magnetometry, the spin axis orientation of the domains was determined with nanometer spatial resolution, and found to depend on the stoichiometry of prepared crystals. © 2023 IEEE.

关键词： Nickel oxide

Constraining the Gravitational Wave Speed in the Early Universe via Gravitational Cherenkov Radiation

学校读者我要写书评

暂无评论

arXiv 2025年

作者： Delgado, Paola C.M. Ganz, Alexander Lin, Chunshan Thériault, Roxane CEICO FZU - Institute of Physics of the Czech Academy of Sciences Na Slovance 1999/2 Prague182 00 Czech Republic Institute for Theoretical Physics Leibniz University Hannover Appelstraße 2 Hannover30167 Germany Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University Krakow30-348 Poland

Scalar particles traveling faster than a subluminal gravitational wave generate gravitons via gravitational Cherenkov radiation. In this paper, we investigate graviton production by the primordial plasma within the framework of modified gravity in the early Universe, generating a relic graviton background. We find that for the minimal model, where only the speed of gravitational waves is modified and a standard model plasma minimally couples to gravity, the relic graviton background can be enhanced by several orders of magnitude, but still agrees with the Big Bang Nucleosynthesis (BBN) bound in most cases. Moreover, we also find that for Horndeski theories, such as Galileon theory, the relic background produced by the thermalized scalar field can reach significant amplitudes, exceeding the BBN bound for a region of the parameter space. By requiring the relic graviton background to remain consistent with the BBN constraint, we derive limits on the gravitational wave speed at early times in these modified gravity theories. Copyright © 2025, The Authors. All rights reserved.

关键词： Gravitational effects

Robust Feature Engineering Techniques for Designing Motor Imagery-Based Bci Systems

学校读者我要写书评

暂无评论

SSRN

SSRN 2025年

作者： Gardezi Ahmed, Syed Saim Khan, Mahnoor Bukhari, Syeda Muneeba Khan, Rizwan Ahmed Jawed, Soyiba Department of Biomedical Engineering Faculty of Engineering Salim Habib University Karachi Pakistan Department of Computer Software Engineering College of Electrical and Mechanical Engineering NUST Islamabad Pakistan Department of Physics Faculty of Applied Sciences Riphah International University Islamabad Pakistan Department of Biomedical Engineering Faculty of Engineering NED University Karachi Pakistan Department of Computer Science Faculty of Information Technology Salim Habib University Karachi Pakistan

A multitude of individuals across the globe grapple with motor disabilities. Neural prosthetics utilizing Brain-computer Interface (BCI) technology exhibit promise for improving motor rehabilitation outcomes. The intricate nature of EEG data poses a significant hurdle for current BCI systems. Recently, a qualitative repository of EEG signals tied to both upper and lower limb execution of motor and motor imagery tasks has been unveiled. Despite this, the productivity of the Machine Learning (ML) Models that were trained on this dataset was alarmingly deficient, and the evaluation framework seemed insufficient. To enhance outcomes, robust feature engineering (signal processing) methodologies are implemented. A collection of time domain, frequency domain, and wavelet-derived features was obtained from 16-channel EEG signals, and the Maximum Relevance Minimum Redundancy (MRMR) approach was employed to identify the four most significant features. For classification K Nearest Neighbors, Support Vector Machine, Decision Tree, and Naive Bayes models were implemented with these selected features, evaluating their effectiveness through metrics such as testing accuracy, precision, recall, and F1 Score. By leveraging SVM with a Gaussian Kernel, a remarkable maximum testing accuracy of 92.50% for motor activities and 95.48% for imagery activities is achieved. These results are notably more dependable and gratifying compared to the previous study, where the peak accuracy was recorded at 74.36%. This research work provide an in-depth analysis of the MI Limb EEG dataset and it will help in designing and developing simple, cost-effective and reliable BCI systems for neuro-rehabilitation. © 2025, The Authors. All rights reserved.

关键词： Image enhancement

Exploring Environmentally Friendly Corrosion Inhibitors: Insights from Natural and Biomass Residue-Derived Compounds

学校读者我要写书评

暂无评论

SSRN

SSRN 2024年

作者： Othman, Norinsan Kamil Mohammed, Naba Jasim Yusop, Muhammed Rahimi Al-Gburi, Ahmed Jamal Abdullah Materials Science Program Department of Applied Physics Faculty of Science and Technology University Kebangsaan Malaysia Selangor Bangi43600 Malaysia Faculty of Science and Technology School of Chemical Sciences and Food Technology University Kepangsaan Malaysia Selangor Bangi43600 Malaysia Faculty of Electronics and Computer Engineering Universiti Teknikal Malaysia Melaka Hang Tuah Jaya Melaka Durian Tunggal76100 Malaysia

In this investigation, we explored the corrosive effects of date palm seed extracted from natural sources and biomass residues on mild steel in a solution of 0.5 M hydrochloric acid (HCl), employing a combination of experimental and theoretical approaches. Our objective was to scrutinize the interaction of the inhibitor with the metal surface, analyze experimental data, and elucidate how the structural characteristics of the inhibitors influence the corrosion process. The experimental results indicated that as the immersion time and temperature increased, the inhibitory effectiveness declined. Notably, the highest level of inhibition occurred when the concentration of date palm seed extract (DPSE) reached 1100 ppm, showcasing peak inhibitory effects of 95.8% and 97.8% through potentiodynamic polarization and electrochemical impedance spectroscopy techniques, respectively. Additionally, an analysis using X-ray diffraction (XRD) was conducted to scrutinize the chemical composition of the mild steel's surface. The adsorption data were evaluated using adsorption isotherms, revealing that DPSE adhered to the Langmuir adsorption isotherm on the mild steel surface. The Langmuir model exhibited the highest linear regression coefficient value and a slope close to unity. The Gibbs free energy () values suggested that the protection afforded by DPSE involved physical and spontaneous absorption. Examination of the results pertaining to the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) indicated that the carboxyl (COOH) group and the C=C bond were the principal regions exhibiting elevated electron acceptance activity. These components were found to be crucial in the adsorption process on the surface of iron (Fe). © 2024, The Authors. All rights reserved.

关键词： Electrochemical impedance spectroscopy

Radiation-dominated bouncing model with slow contraction and inflation

学校读者我要写书评

暂无评论

Physical Review D 2024年第4期109卷 043531-043531页

作者： Piero A. P. Molinari Paola C. M. Delgado Rodrigo F. Pinheiro Nelson Pinto-Neto Centro Brasileiro de Pesquisas Físicas - CBPF Rua Dr. Xavier Sigaud 150 Urca 22290-180 Rio de Janeiro RJ Brazil Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University 30-348 Krakow Poland

A very simple nonsingular inflationary model is presented where the unique matter content is a radiation fluid. The model slowly contracts from a very large, almost empty and flat spacetime and realizes a bounce. It is then launched to a quasi-de Sitter inflationary expansion with more than sixty e-folds, which smoothly changes to the usual classical, decelerated radiation-dominated expansion before nucleosynthesis. The initial contracting and final expanding phases are classical, but the intermediate bounce and inflationary phases are induced by quantum cosmological effects emerging from a Gaussian wave function quickly moving in configuration space. During this quantum era, a huge number of photons is created. The scale factor describing all this rich evolution is a surprisingly simple analytic function of conformal time. The cosmological scalar perturbations arising from quantum vacuum fluctuations in the far past of the model present an almost scale invariant spectrum with an amplitude compatible with observations for reasonable values of the free parameters of the model.

关键词： Canonical quantum gravity Cosmology Inflation Quantum cosmology

Enhancement and anisotropy of electron Landé factor due to spin-orbit interaction in semiconductor nanowires

学校读者我要写书评

暂无评论

arXiv 2023年

作者： Czarnecki, Julian Bertoni, Andrea Goldoni, Guido Wójcik, Pawel AGH University of Krakow Faculty of Physics and Applied Computer Science al. A. Mickiewicza 30 Krakow30-059 Poland CNR-NANO S3 Istituto Nanoscienze Via Campi 213/a Modena41125 Italy Department of Physics Informatics and Mathematics University of Modena and Reggio Emilia via Campi 213/a Modena41125 Italy

We investigate the effective Landé factor in semiconductor nanowires with strong Rashba spin-orbit coupling. Using the k · p theory and the envelope function approach we derive a conduction band Hamiltonian where g∗ is explicitly related to the spin-orbit coupling contants αR. Our model includes orbital effects from the Rashba spin-orbit term, leading to a significant enhancement of the effective Landé factor which is naturally anisotropic. For nanowires based on the low-gap, high spin-orbit coupled material InSb, we investigate the anisotropy of the effective Landé factor with respect to the magnetic field direction, exposing a twofold symmetry for the bottom gate architecture. The anisotropy results from the competition between the localization of the envelope function and the spin polarization of the electronic state, both determined by the magnetic field direction. Copyright © 2023, The Authors. All rights reserved.

关键词： Anisotropy