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Emergent superconductivity and non-reciprocal transport in a van der Waals Dirac semimetal/antiferromagnet heterostructure

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arXiv 2025年

作者： Islam, Saurav Stanley, Max Richardella, Anthony Lee, Seungjun Halanayake, Kalana D. Santhosh, Sandra Hickey, Danielle Reifsnyder Low, Tony Samarth, Nitin Department of Physics Pennsylvania State University University ParkPA16802 United States Materials Research Institute Pennsylvania State University University ParkPA16802 United States Department of Electrical and Computer Engineering University of Minnesota MinneapolisMN55455 United States Department of Chemistry Pennsylvania State University University ParkPA16802 United States Department of Materials Science and Engineering Pennsylvania State University University ParkPA16802 United States School of Physics and Astronomy University of Minnesota MinneapolisMN55455 United States

We investigate emergent superconductivity and non-reciprocal transport (magnetochiral anisotropy, superconducting diode effect) at the heterointerface of two non-superconducting van der Waals (vdW) materials, the Dirac semimetal ZrTe2 and the antiferromagnetic iron chalcogenide FeTe, grown using molecular beam epitaxy. We show from electrical transport measurements that two dimensional (2D) superconductivity arises at the heterointerface below temperature T ∼ 12 K. When capped with a 2D ferromagnet (CrTe2), these heterostructures show a superconducting diode effect with efficiency of about 30%. With strong spin-orbit coupling in ZrTe2, these epitaxial heterostructures provide an attractive epitaxial vdW platform for exploring unconventional superconductivity in Dirac semimetals and for developing non-reciprocal devices for superconducting electronics. © 2025, CC BY.

关键词： Van der Waals forces

Influence of Tm and Tb co-substitution on structural and magnetic features of CoFe₂O₄ nanospinel ferrites

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Nano-Structures and Nano-Objects 2023年 33卷

作者： Akhtar, S. Slimani, Y. Almessiere, M.A. Baykal, A. Polat, E. Gokce Caliskan, S. Department of Biophysics Institute for Research and Medical Consultations (IRMC) Imam Abdulrahman Bin Faisal University P.O. Box 1982 Dammam 31441 Saudi Arabia Department of Physics College of Science Imam Abdulrahman Bin Faisal University P.O. Box 1982 Dammam 31441 Saudi Arabia Department of Nano-Medicine Research Institute for Research and Medical Consultations (IRMC) Imam Abdulrahman Bin Faisal University P.O. Box 1982 Dammam 31441 Saudi Arabia Department of Engineering Physics Istanbul Medeniyet University 34700 Uskudar-Istanbul Turkey Department of Electrical and Computer Engineering University of Minnesota 200 Union St. SE Minneapolis 55455 MN United States Department of Physical and Applied Sciences University of Houston-Clear Lake Houston 77058 TX United States

Tm-Tb co-substituted CoFe 2O4 nanospinel ferrites (CoTm xTbxFe2−2xO4, CoTmTb (x = 0.00– 0.03) NSFs)) were prepared via a sonochemical chemical route. The microstructures and morphologies of the NSFs were investigated... 详细信息

Tm-Tb co-substituted CoFe ₂O₄ nanospinel ferrites (CoTm _xTb_xFe_2−2xO₄, CoTmTb (x = 0.00– 0.03) NSFs)) were prepared via a sonochemical chemical route. The microstructures and morphologies of the NSFs were investigated via XRD, SAED and TEM/SEM, along with EDX techniques. The XRD analysis confirmed the cubic structure all the products along with the absence of any impurities. All the crystallite sizes were observed to be within the range of 9–11 nm. Electron microscopy techniques (SEM, TEM and HR-TEM) proved a cubic morphology in each case and their chemical compositions were confirmed by EDX. The magnetic properties of the synthesized NSFs were investigated via VSM through analysis of the magnetization versus applied magnetic field data. The M–H studies were made at 10 and 300 K. All the NSFs displayed soft ferrimagnetic behavior. It was observed that Tb³⁺ and Tm³⁺ ions substitutions provoke substantial variations in the magnetic behavior of the host CoFe ₂O₄ system. Upon doping the CoFe ₂O₄ system with the Tb³⁺ and Tm³⁺ ions, the magnetic features, M_s (saturation) and M_r (remanent) as well as the H_c (coercive field), increased for x=0.010 and then started to decrease gradually with a further increase in the dopant contents (Tb³⁺ and Tm³⁺ ions). The exchange interactions between the cations distributed over the A and B sites is one of the main reasons for the observed evolution in the magnetization magnitudes with the composition. Other factors, like strain, surface spins disorder, crystallite size, size of magnetic domains and Bohr magneton number, were also reported in order to explain the variations in diverse magnetic parameters. © 2023 Elsevier B.V.

关键词： CoFe2O4 nanospinel ferrites Magnetic properties Sonochemical synthesis Spinel ferrites

Resonant beam communications with echo interference elimination

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arXiv 2021年

作者： Xiong, Mingliang Liu, Qingwen Wang, Gang Giannakis, Georgios B. Zhang, Sihai Zhu, Jinkang Huang, Chuan College of Electronics and Information Engineering Tongji University Shanghai201804 China State Key Lab of Intelligent Control and Decision of Complex Systems School of Automation Beijing Institute of Technology Beijing100081 China Department of Electrical and Computer Engineering University of Minnesota MinneapolisMN55455 United States Key Lab of Wireless-Optical Communications University of Science and Technology of China Hefei Anhui230026 China School of Science and Engineering Chinese University of Hong Kong Shenzhen Guangdong518172 Hong Kong

Resonant beam communications (RBCom) is capable of providing wide bandwidth when using light as the carrier. Besides, the RBCom system possesses the characteristics of mobility, high signal-to-noise ratio (SNR), and multiplexing. Nevertheless, the channel of the RBCom system is distinct from other light communication technologies due to the echo interference issue. In this paper, we reveal the mechanism of the echo interference and propose the method to eliminate the interference. Moreover, we present an exemplary design based on frequency shifting and optical filtering, along with its mathematic model and performance analysis. The numerical evaluation shows that the channel capacity is greater than 15 bit/s/Hz. Copyright © 2021, The Authors. All rights reserved.

关键词： Internet of things

Impact of surface roughness in nanogap plasmonic systems

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arXiv 2020年

作者： Cirací, Cristian Vidal-Codina, Ferran Yoo, Daehan Peraire, Jaime Oh, Sang-Hyun Smith, David R. Center for Biomolecular Nanotechnologies Istituto Italiano di Tecnologia Via Barsanti Arnesano73010 Italy Department of Aeronautics and Astronautics Massachusetts Institute of Technology CambridgeMA02139 United States Department of Electrical and Computer Engineering University of Minnesota MinneapolisMN55455 United States Center for Metamaterial and Integrated Plasmonics Department of Electrical and Computer Engineering Pratt School of Engineering Duke University DurhamNC27708 United States

Recent results have shown unprecedented control over separation distances between two metallic elements hundreds of nanometers in size, underlying the effects of free-electron nonlocal response also at mid-infrared wavelengths. Most of metallic systems however, still suffer from some degree of inhomogeneity due to fabrication-induced surface roughness. Nanoscale roughness in such systems might hinder the understanding of the role of microscopic interactions. Here we investigate the effect of surface roughness in coaxial nanoapertures resonating at mid-infrared frequencies. We show that although random roughness shifts the resonances in an unpredictable way, the impact of nonlocal effects can still be clearly observed. Roughness-induced perturbation on the peak resonance of the system shows a strong correlation with the effective gap size of the individual samples. Fluctuations due to fabrication imperfections then can be suppressed by performing measurements on structure ensembles in which averaging over a large number of samples provides a precise measure of the ideal systems optical properties. Copyright © 2020, The Authors. All rights reserved.

关键词： Surface roughness

Topology attack and defense for graph neural networks: An optimization perspective

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arXiv 2019年

作者： Xu, Kaidi Chen, Hongge Liu, Sijia Chen, Pin-Yu Weng, Tsui-Wei Hong, Mingyi Lin, Xue Electrical & Computer Engineering Northeastern University Boston United States Electrical Engineering & Computer Science Massachusetts Institute of Technology Cambridge United States MIT-IBM Watson AI Lab IBM Research Electrical & Computer Engineering University of Minnesota Minneapolis United States

Graph neural networks (GNNs) which apply the deep neural networks to graph data have achieved significant performance for the task of semi-supervised node classification. However, only few work has addressed the adversarial robustness of GNNs. In this paper, we first present a novel gradient-based attack method that facilitates the difficulty of tackling discrete graph data. When comparing to current adversarial attacks on GNNs, the results show that by only perturbing a small number of edge perturbations, including addition and deletion, our optimization-based attack can lead to a noticeable decrease in classification performance. Moreover, leveraging our gradient-based attack, we propose the first optimization-based adversarial training for GNNs. Our method yields higher robustness against both different gradient based and greedy attack methods without sacrificing classification accuracy on original graph. Code is available at https://***/KaidiXu/GCN_ADV_Train. Copyright © 2019, The Authors. All rights reserved.

关键词： Graph neural networks

Quantization Games on Social Networks and Language Evolution

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arXiv 2020年

作者： Mani, Ankur Varshney, Lav R. Pentland, Alex Department of Industrial & Systems Engineering University of Minnesota MinneapolisMN55455 United States Coordinated Science Laboratory Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign UrbanaIL61801 United States Media Laboratory Massachusetts Institute of Technology CambridgeMA02139 United States

We consider a strategic network quantizer design setting where agents must balance fidelity in representing their local source distributions against their ability to successfully communicate with other connected agents. We study the problem as a network game and show existence of Nash equilibrium quantizers. For any agent, under Nash equilibrium, the word representing a given partition region is the conditional expectation of the mixture of local and social source probability distributions within the region. Since having knowledge of the original source of information in the network may not be realistic, we show that under certain conditions, the agents need not know the source origin and yet still settle on a Nash equilibrium using only the observed sources. Further, the network may converge to equilibrium through a distributed version of the Lloyd-Max algorithm. In contrast to traditional results in the evolution of language, we find several vocabularies may coexist in the Nash equilibrium, with each individual having exactly one of these vocabularies. The overlap between vocabularies is high for individuals that communicate frequently and have similar local sources. Finally, we argue that error in translation along a chain of communication does not grow if and only if the chain consists of agents with shared vocabulary. Numerical results are given. Copyright © 2020, The Authors. All rights reserved.

关键词： Game theory

Transport studies in a gate-tunable three-terminal Josephson junction

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Physical Review B 2020年第5期101卷 054510-054510页

作者： Gino V. Graziano Joon Sue Lee Mihir Pendharkar Chris J. Palmstrøm Vlad S. Pribiag School of Physics and Astronomy University of Minnesota Minneapolis Minneapolis 55455 USA California NanoSystems Institute University of California Santa Barbara Santa Barbara California 93106 USA Electrical and Computer Engineering University of California Santa Barbara Santa Barbara California 93106 USA Materials Department University of California Santa Barbara Santa Barbara California 93106 USA

Josephson junctions with three or more superconducting leads have been predicted to exhibit topological effects in the presence of few conducting modes within the interstitial normal material. Such behavior, of relevance for topologically protected quantum bits, would lead to specific transport features measured between terminals, with topological phase transitions occurring as a function of phase and voltage bias. Although conventional, two-terminal Josephson junctions have been studied extensively, multiterminal devices have received relatively little attention to date. Motivated in part by the possibility to ultimately observe topological phenomena in multiterminal Josephson devices, as well as their potential for coupling gatemon qubits, here we describe the superconducting features of a top-gated mesoscopic three-terminal Josephson device. The device is based on an InAs two-dimensional electron gas proximitized by epitaxial aluminum. We map out the transport properties of the device as a function of bias currents, top gate voltage, and magnetic field. We find a very good agreement between the zero-field experimental phase diagram and a resistively and capacitively shunted junction computational model.

关键词： Josephson effect Mesoscopics Superconductivity Transport phenomena Devices III-V semiconductors Josephson junctions Narrow band gap systems Quantum wells Topological materials Two-dimensional electron system Dilution refrigerator Evaporation Lithography Molecular beam epitaxy Resistivity measurements

A virtual network customization framework for multicast services in NFV-enabled core networks

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arXiv 2020年

作者： Alhussein, Omar Do, Phu Thinh Ye, Qiang Li, Junling Shi, Weisen Zhuang, Weihua Shen, Xuemin Li, Xu Rao, Jaya Department of Electrical and Computer Engineering University of Waterloo WaterlooONN2L 3G1 Canada Institute of Research and Development Duy Tan University Da Nang550000 Viet Nam Department of Electrical and Computer Engineering and Technology Minnesota State University MankatoMN56001 United States Huawei Technologies Canada Inc. OttawaONK2K 3J1 Canada

The paradigm of network function virtualization (NFV) with the support of software defined networking (SDN) emerges as a promising approach for customizing network services in fifth generation (5G) networks. In this paper, a multicast service orchestration framework is presented, where joint traffic routing and virtual network function (NF) placement are studied for accommodating multicast services over an NFV-enabled physical substrate network. First, we investigate a joint routing and NF placement problem for a single multicast request accommodated over a physical substrate network, with both single-path and multipath traffic routing. The joint problem is formulated as a mixed integer linear programming (MILP) problem to minimize the function and link provisioning costs, under the physical network resource constraints, flow conservation constraints, and NF placement rules;Second, we develop an MILP formulation that jointly handles the static embedding of multiple service requests over the physical substrate network, where we determine the optimal combination of multiple services for embedding and their joint routing and placement configurations, such that the aggregate throughput of the physical substrate is maximized, while the function and link provisioning costs are minimized. Since the presented problem formulations are NP-hard, low complexity heuristic algorithms are proposed to find an efficient solution for both single-path and multipath routing scenarios. Simulation results are presented to demonstrate the effectiveness and accuracy of the proposed heuristic algorithms. Copyright © 2020, The Authors. All rights reserved.

关键词： 5G mobile communication systems

Ultralight dark matter detection with levitated ferromagnets

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arXiv 2024年

作者： Kalia, Saarik Budker, Dmitry Jackson Kimball, Derek F. Ji, Wei Liu, Zhen Sushkov, Alexander O. Timberlake, Chris Ulbricht, Hendrik Vinante, Andrea Wang, Tao School of Physics & Astronomy University of Minnesota MinneapolisMN55455 United States Johannes Gutenberg University Mainz Mainz55128 Germany Helmholtz-Institute GSI Helmholtzzentrum fur Schwerionenforschung Mainz55128 Germany Department of Physics University of California at Berkeley BerkeleyCA94720-7300 United States Department of Physics California State University – East Bay HaywardCA94542 United States Department of Physics Boston University BostonMA02215 United States Department of Electrical and Computer Engineering Boston University BostonMA02215 United States Photonics Center Boston University BostonMA02215 United States School of Physics and Astronomy University of Southampton SouthamptonSO17 1BJ United Kingdom Istituto di Fotonica e Nanotecnologie IFN–CNR Povo Trento38123 Italy Povo Trento38123 Italy 2 Fusionopolis Way 08-03 Singapore138634 Singapore

Levitated ferromagnets act as ultraprecise magnetometers, which can exhibit high quality factors due to their excellent isolation from the environment. These instruments can be utilized in searches for ultralight dark matter candidates, such as axionlike dark matter or dark-photon dark matter. In addition to being sensitive to an axion-photon coupling or kinetic mixing, which produce physical magnetic fields, ferromagnets are also sensitive to the effective magnetic field (or "axion wind") produced by an axion-electron coupling. While the dynamics of a levitated ferromagnet in response to a DC magnetic field have been well studied, all of these couplings would produce AC fields. In this work, we study the response of a ferromagnet to an applied AC magnetic field and use these results to project their sensitivity to axion and dark-photon dark matter. We pay special attention to the direction of motion induced by an applied AC field, in particular, whether it precesses around the applied field (similar to an electron spin) or librates in the plane of the field (similar to a compass needle). We show that existing levitated ferromagnet setups can already have comparable sensitivity to an axion-electron coupling as comagnetometer or torsion balance experiments. In addition, future setups can become sensitive probes of axion-electron coupling, dark-photon kinetic mixing, and axion-photon coupling, for ultralight dark matter masses mDM feV. © 2024, CC BY-NC-SA.

关键词： Photons