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arXiv 2020年

作者： Puglia, D. Martinez, E.A. Ménard, G.C. Pöschl, A. Gronin, S. Gardner, G.C. Kallaher, R. Manfra, M.J. Marcus, C.M. Higginbotham, A.P. Casparis, L. Microsoft Quantum Labs Copenhagen Center for Quantum Devices Niels Bohr Institute University of Copenhagen Universitetsparken 5 Copenhagen2100 Denmark Institute of Science and Technology Austria Am Campus 1 Klosterneuburg3400 Austria Microsoft Quantum Purdue Birck Nanotechnology Center Purdue University West LafayetteIN United States Department of Physics and Astronomy Purdue University West LafayetteIN United States School of Materials Engineering Purdue University West LafayetteIN United States School of Electrical and Computer Engineering Purdue University West LafayetteIN United States

Hybrid superconductor-semiconductor nanowires are predicted to undergo a field-induced phase transition from a trivial to a topological superconductor, marked by the closure and re-opening of the excitation gap, followed by the emergence of Majorana bound states at the nanowire ends [1, 2]. Many local density-of-states measurements have reported signatures of the topological phase [3], however this interpretation has been challenged by alternative explanations [4–10]. Here, by measuring nonlocal conductance, we identify the closure of the excitation gap in the bulk of the semiconductor before the emergence of zero-bias peaks. This observation is inconsistent with scenarios where zero-bias peaks occur due to end-states with a trivially gapped bulk, which have been extensively considered in the theoretical [4–10] and experimental [11–13] literature. We observe that after the gap closes, nonlocal signals fluctuate strongly and persist irrespective of the presence of local-conductance zero-bias peaks. Thus, our observations are also incompatible with a simple picture of clean topological superconductivity [1, 2]. This work presents a new experimental approach for probing the spatial extent of states in Majorana wires, and reveals the presence of a regime with a continuum of spatially extended states and uncorrelated zero-bias peaks. Copyright © 2020, The Authors. All rights reserved.

关键词： Nanowires

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Correlator convolutional neural networks: an interpretable architecture for image-like quantum matter data

arXiv

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arXiv 2020年

作者： Miles, Cole Bohrdt, Annabelle Wu, Ruihan Chiu, Christie Xu, Muqing Ji, Geoffrey Greiner, Markus Weinberger, Kilian Q. Demler, Eugene Kim, Eun-Ah Department of Physics Cornell University IthacaNY14853 United States Department of Physics Harvard University CambridgeMA02138 United States Department of Physics Institute for Advanced Study India Technical University of Munich Garching85748 Germany München80799 Germany Department of Computer Science Cornell University IthacaNY14853 United States Department of Electrical Engineering Princeton University PrincetonNJ08540 United States Princeton Center for Complex Materials Princeton University PrincetonNJ08540 United States

Machine learning models are a powerful theoretical tool for analyzing data from quantum simulators, in which results of experiments are sets of snapshots of many-body states. Recently, they have been successfully applied to distinguish between snapshots that can not be identified using traditional one and two point correlation functions. Thus far, the complexity of these models has inhibited new physical insights from this approach. Here, using a novel set of nonlinearities we develop a network architecture that discovers features in the data which are directly interpretable in terms of physical observables. In particular, our network can be understood as uncovering high-order correlators which significantly differ between the data studied. We demonstrate this new architecture on sets of simulated snapshots produced by two candidate theories approximating the doped Fermi-Hubbard model, which is realized in state-of-the art quantum gas microscopy experiments. From the trained networks, we uncover that the key distinguishing features are fourth-order spin-charge correlators, providing a means to compare experimental data to theoretical predictions. Our approach lends itself well to the construction of simple, end-to-end interpretable architectures and is applicable to arbitrary lattice data, thus paving the way for new physical insights from machine learning studies of experimental as well as numerical data. Copyright © 2020, The Authors. All rights reserved.

关键词： Correlators

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Extreme sub-wavelength light confinement in plasmonic film-coupled nanostar resonators

arXiv

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arXiv 2019年

作者： Charchi, Negar Li, Ying Huber, Margaret Kwizera, Elyahb Allie Huang, Xiaohua Argyropoulos, Christos Hoang, Thang Department of Physics and Materials Science University of Memphis MemphisTN38152 United States Department of Electrical and Computer Engineering University of Nebraska-Lincoln LincolnNE68588 United States Department of Chemistry University of Memphis MemphisTN38152 United States

Confining light in extreme subwavelength scales is a tantalizing task. In this work, we report a study of individual plasmonic film-coupled nanostar resonators where plasmonic optical modes are trapped in ultrasmall volumes. Individual gold nanostars, separated from a flat gold film by a thin dielectric spacer layer, exhibit a strong light confinement between the sub-10 nm volume of the nanostar’s tips and the film. Through dark field scattering measurements of many individual nanostars, a statistical observation of the scattered spectra is obtained and compared with extensive simulation data to reveal the origins of the resonant peaks. We observe that an individual nanostar on a flat gold film can result in a resonant spectrum with single, double or multiple peaks. Further, these resonant peaks are strongly polarized under white light illumination. Our simulation data revealed that the resonant spectrum of an individual film-coupled nanostar resonator is related to the symmetry of the nanostar, as well as the orientation of the nanostar relative to its placement on the gold substrate. Our results demonstrate a simple method to create an ultrasmall mode volume plasmonic platform which could be useful for applications in sensing or enhanced light-matter interactions. Copyright © 2019, The Authors. All rights reserved.

关键词： Plasmonics

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Macroscopically aligned carbon nanotubes as a refractory platform for hyperbolic thermal emitters

arXiv

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arXiv 2019年

作者： Gao, Weilu Doiron, Chloe F. Li, Xinwei Kono, Junichiro Naik, Gururaj V. Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Department of Physics and Astronomy Rice University HoustonTX77005 United States Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States

Refractory nanophotonics, or nanophotonics at high temperatures, can revolutionize many applications, including data storage and waste heat recovery. In particular, nanophotonic devices made from hyperbolic materials are promising due to their nearly infinite photonic density of states (PDOS). However, it is challenging to achieve a prominent PDOS in existing refractory hyperbolic materials, especially in a broad spectral range. Here, we demonstrate that macroscopic films and architectures of aligned carbon nanotubes work as excellent refractory hyperbolic materials. We found that aligned carbon nanotubes are thermally stable up to 1600 ◦C and exhibit extreme anisotropy - metallic in one direction and insulating in the other two directions. Such extreme anisotropy makes this system a hyperbolic material with an exceptionally large PDOS over a broadband spectrum range (longer than 4.3 µm) in the midinfrared, exhibiting strong resonances in deeply subwavelength-sized cavities. We observed polarized, spectrally selective thermal emission from aligned carbon nanotube films as well as indefinite cavities of aligned carbon nanotubes with volume as small as ∼ λ3/700 operating at 700 ◦C. These experiments suggest that aligned carbon nanotubes possess naturally large PDOS that leads to thermal photon densities enhanced by over two orders of magnitude, making them a promising refractory nanophotonics platform. Copyright © 2019, The Authors. All rights reserved.

关键词： Anisotropy

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Interplay between effects of barrier tilting and scatterers within a barrier on tunneling transport of Dirac electrons in graphene

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Physical Review B 2020年第11期101卷 115424-115424页

作者： Farhana Anwar Andrii Iurov Danhong Huang Godfrey Gumbs Ashwani Sharma Center for High Technology Materials University of New Mexico 1313 Goddard SE Albuquerque New Mexico 87106 USA Department of Electrical and Computer Engineering University of New Mexico Albuquerque New Mexico 87106 USA Department of Physics and Computer Science Medgar Evers College of City University of New York Brooklyn New York 11225 USA Air Force Research Laboratory Space Vehicles Directorate Kirtland Air Force Base New Mexico 87117 USA Department of Physics and Astronomy Hunter College of the City University of New York 695 Park Avenue New York New York 10065 USA Donostia International Physics Center (DIPC) P de Manuel Lardizabal 4 20018 San Sebastian Basque Country Spain

Dirac-electronic tunneling and transport properties with both finite and zero energy band gap are investigated for graphene with an in-plane tilted potential barrier embedded with scatters. For a tilted barrier, by using Wentzel-Kramers-Brillouin approximation, an analytical solution is obtained first for transmission coefficient of Dirac electrons in gapped graphene in the absence of any scatters. In the presence of either a single or a continuous distribution of scatters embedded within a tilted barrier, however, a numerical scheme based on finite-difference approach is developed for accurately calculating both transmission coefficient and tunneling resistance of Dirac electrons. Here, the combination of a tilted barrier and a scatter potential can be viewed as an effective barrier-potential profile facilitated by a proper gate structure. Meanwhile, a full analysis and detailed comparisons are presented for the interplay between effects of both distributed scatters in a barrier and barrier tilting on tunneling transport of Dirac electrons in graphene. The barrier-tilting field and scatter position are found to play a key role in controlling a peak of tunneling resistance as well as in its switching to a cusp by a mid-barrier-embedded scatter as the incident energy reaches the Dirac point in a barrier. Different from a single scatter, a continuous distribution within a barrier can enhance the unimpeded incoherent tunneling for head-on collision while greatly suppressing skew ones with increasing barrier-tilting field. All these predicted attractive transport properties are expected to be extremely useful for designing both novel electronic and optical graphene-based devices and electronic lenses in ballistic-electron optics.

关键词： electrical conductivity Graphene Tunnel junctions

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Highly Reversible Aqueous Zinc Batteries enabled by Zincophilic–Zincophobic Interfacial Layers and Interrupted Hydrogen-Bond Electrolytes

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Angewandte Chemie 2021年第34期133卷

作者： Dr. Longsheng Cao Dr. Dan Li Dr. Fernando A. Soto Dr. Victor Ponce Dr. Bao Zhang Dr. Lu Ma Dr. Tao Deng Dr. Jorge M. Seminario Dr. Enyuan Hu Dr. Xiao-Qing Yang Prof. Perla B. Balbuena Prof. Chunsheng Wang Department of Chemical and Biomolecular Engineering University of Maryland College Park MD 20742 USA Department of Chemical Engineering Texas A&M University College Station TX 77843 USA National Synchrotron Light Source II Brookhaven National Laboratory Upton NY 11973 USA Department of Materials Science and Engineering Texas A&M University College Station TX 77843 USA Department of Electrical and Computer Engineering Texas A&M University College Station TX 77843 USA Chemistry Division Brookhaven National Laboratory Upton NY 11973 USA

Aqueous Zn batteries promise high energy density but suffer from Zn dendritic growth and poor low-temperature performance. Here, we overcome both challenges by using an eutectic 7.6 m ZnCl 2 aqueous electrolyte with 0.05 m SnCl 2 additive, which in situ forms a zincophilic/zincophobic Sn/Zn 5 (OH) 8 Cl 2 ⋅H 2 O bilayer interphase and enables low temperature operation. Zincophilic Sn decreases Zn plating/stripping overpotential and promotes uniform Zn plating, while zincophobic Zn 5 (OH) 8 Cl 2 ⋅H 2 O top-layer suppresses Zn dendrite growth. The eutectic electrolyte has a high ionic conductivity of ≈0.8 mS cm −1 even at −70 °C due to the distortion of hydrogen bond network by solvated Zn 2+ and Cl − . The eutectic electrolyte enables Zn∥Ti half-cell a high Coulombic efficiency (CE) of >99.7 % for 200 cycles and Zn∥Zn cell steady charge/discharge for 500 h with a low overpotential of 8 mV at 3 mA cm −2 . Practically, Zn∥VOPO 4 batteries maintain >95 % capacity with a CE of >99.9 % for 200 cycles at −50 °C, and retain ≈30 % capacity at −70 °C of that at 20 °C.

关键词： aqueous zinc batteries hydrogen bonds low temperature salt precipitation zincophilic–zincophobic interfacial bilayer

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Weak antilocalization in quasi-two-dimensional electronic states of epitaxial LuSb thin films

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Physical Review B 2019年第12期99卷 125134-125134页

作者： Shouvik Chatterjee Shoaib Khalid Hadass S. Inbar Aranya Goswami Felipe Crasto de Lima Abhishek Sharan Fernando P. Sabino Tobias L. Brown-Heft Yu-Hao Chang Alexei V. Fedorov Dan Read Anderson Janotti Christopher J. Palmstrøm Department of Electrical & Computer Engineering University of California Santa Barbara California 93106 USA Department of Physics and Astronomy University of Delaware Newark Delaware 19716 USA Department of Materials Science and Engineering University of Delaware Newark Delaware 19716 USA Materials Department University of California Santa Barbara California 93106 USA Advanced Light Source Lawrence Berkeley National Laboratory Berkeley California 94720 USA School of Physics and Astronomy Cardiff University Cardiff CF24 3AA United Kingdom

Observation of large nonsaturating magnetoresistance in rare-earth monopnictides has raised enormous interest in understanding the role of its electronic structure. Here, by a combination of molecular-beam epitaxy, low-temperature transport, angle-resolved photoemission spectroscopy, and hybrid density functional theory we have unveiled the band structure of LuSb, where electron-hole compensation is identified as a mechanism responsible for large magnetoresistance in this topologically trivial compound. In contrast to bulk single crystal analogues, quasi-two-dimensional behavior is observed in our thin films for both electron and holelike carriers, indicative of dimensional confinement of the electronic states. Introduction of defects through growth parameter tuning results in the appearance of quantum interference effects at low temperatures, which has allowed us to identify the dominant inelastic scattering processes and elucidate the role of spin-orbit coupling. Our findings open up possibilities of band structure engineering and control of transport properties in rare-earth monopnictides via epitaxial synthesis.

关键词： Density of states Electronic structure Fermi surface First-principles calculations Phonons Spin-orbit coupling Topological materials

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Spatially resolved steady-state negative capacitance (vol 565, pg 468, 2019)

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NATURE 2019年第7753期568卷 E13-E13页

作者： Yadav, Ajay K. Nguyen, Kayla X. Hong, Zijian Garcia-Fernandez, Pablo Aguado-Puente, Pablo Nelson, Christopher T. Das, Sujit Prasad, Bhagwati Kwon, Daewoong Cheema, Suraj Khan, Asif I. Hu, Chenming Iniguez, Jorge Junquera, Javier Chen, Long-Qing Muller, David A. Ramesh, Ramamoorthy Salahuddin, Sayeef Department of Electrical Engineering and Computer Sciences University of California Berkeley USA Department of Chemistry and Chemical Biology Cornell University Ithaca USA Department of Materials Science and Engineering Pennsylvania State University State College USA Departamento de Ciencias de la Tierra y Física de la Materia Condensada Universidad de Cantabria Cantabria Campus Internacional Santander Spain Atomistic Simulation Centre Queen’s University Belfast Belfast UK National Center for Electron Microscopy Lawrence Berkeley Laboratory Berkeley USA Department of Materials Science and Engineering University of California Berkeley USA School of Electrical and Computer Engineering Georgia Institute of Technology Atlanta USA Materials Research and Technology Department Luxembourg Institute of Science and Technology Esch/Alzette Luxembourg School of Applied and Engineering Physics Cornell University Ithaca USA Kavli Institute at Cornell for Nanoscale Science Cornell University Ithaca USA

In this Letter, the first name of author Bhagwati Prasad was misspelled Bhagawati. This error has been corrected online.

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Dynamic exciton funneling by local strain control in a monolayer semiconductor

arXiv

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arXiv 2019年

作者： Moon, Hyowon Grosso, Gabriele Chakraborty, Chitraleema Peng, Cheng Taniguchi, Takashi Watanabe, Kenji Englund, Dirk Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology CambridgeMA United States Photonics Initiative Advanced Science Research Center City University of New York New YorkNY United States National Institute for Materials Science Tsukuba Ibaraki Japan

The ability to control excitons in semiconductors underlies numerous proposed applications, from excitonic circuits for computing and communications1,2 to polariton condensates3 to energy transport in photovoltaics4. 2D semiconductors are particularly promising for room-temperature applications due to their large exciton binding energy5,6. Their enormous stretchability gives rise to a strain-engineerable bandgap that has been used to induce static exciton flux in predetermined structures7-10. However, dynamic control of exciton flux represents an outstanding challenge. Here, we introduce a method to tune the bandgap of suspended 2D semiconductors by applying a local strain gradient with a nanoscale tip. This strain allows us to locally and reversibly shift the exciton energy and to steer the exciton flux over micron-scale distances, as observed by wide-field imaging and time-resolved photoluminescence spectroscopy. We anticipate that the ability to strongly and dynamically modulate the bandgap of a semiconductor at the nanoscale not only marks an important experimental tool but will also open a broad range of new applications from information processing to energy conversion. Copyright © 2019, The Authors. All rights reserved.

关键词： Energy gap

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A mountable toilet system for personalized health monitoring via the analysis of excreta (vol 15, pg 561, 2020)

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NATURE BIOMEDICAL engineering 2020年第6期4卷 662-662页

作者： Park, Seung-min Won, Daeyoun D. Lee, Brian J. Escobedo, Diego Esteva, Andre Aalipour, Amin Ge, T. Jessie Kim, Jung Ha Suh, Susie Choi, Elliot H. Lozano, Alexander X. Yao, Chengyang Bodapati, Sunil Achterberg, Friso B. Kim, Jeesu Park, Hwan Choi, Youngjae Kim, Woo Jin Yu, Jung Ho Bhatt, Alexander M. Lee, Jong Kyun Spitler, Ryan Wang, Shan X. Gambhir, Sanjiv S. Department of Radiology Stanford University School of Medicine Stanford CA USA Molecular Imaging Program at Stanford Stanford University School of Medicine Stanford CA USA Department of Surgery Seoul Song Do Hospital Seoul Republic of Korea Cancer Immunology Laboratory Seoul Song Do Hospital Seoul Republic of Korea Department of Surgery Leiden University Medical Center Leiden the Netherlands Department of Creative IT Engineering Pohang University of Science and Technology (POSTECH) Pohang Republic of Korea Precision Health and Integrated Diagnostic Center (PHIND) Stanford University School of Medicine Palo Alto CA USA Department of Materials Science and Engineering Stanford University Stanford CA USA Department of Bioengineering Stanford University Stanford CA USA Canary Center at Stanford for Cancer Early Detection Stanford University School of Medicine Palo Alto CA USA Salesforce Research Palo Alto CA USA Department of Urology Stanford University School of Medicine Stanford CA USA Department of Pharmacology Case Western Reserve University School of Medicine Cleveland OH USA Faculty of Medicine University of Toronto Toronto Ontario Canada Department of Electrical Engineering Stanford University Stanford CA USA College of Medicine The Catholic University of Korea Seoul Republic of Korea

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

关键词： Diagnosis

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