| 11. |
- Drexler, C., et al.
(författare)
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Magnetic quantum ratchet effect in graphene
- 2013
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Ingår i: Nature Nanotechnology. - 1748-3387 .- 1748-3395. ; 8:2, s. 104-107
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Tidskriftsartikel (refereegranskat)abstract
- A periodically driven system with spatial asymmetry can exhibit a directed motion facilitated by thermal or quantum fluctuations(1). This so-called ratchet effect(2) has fascinating ramifications in engineering and natural sciences(3-18). Graphene(19) is nominally a symmetric system. Driven by a periodic electric field, no directed electric current should flow. However, if the graphene has lost its spatial symmetry due to its substrate or adatoms, an electronic ratchet motion can arise. We report an experimental demonstration of such an electronic ratchet in graphene layers, proving the underlying spatial asymmetry. The orbital asymmetry of the Dirac fermions is induced by an in-plane magnetic field, whereas the periodic driving comes from terahertz radiation. The resulting magnetic quantum ratchet transforms the a.c. power into a d.c. current, extracting work from the out-of-equilibrium electrons driven by undirected periodic forces. The observation of ratchet transport in this purest possible two-dimensional system indicates that the orbital effects may appear and be substantial in other two-dimensional crystals such as boron nitride, molybdenum dichalcogenides and related heterostructures. The measurable orbital effects in the presence of an in-plane magnetic field provide strong evidence for the existence of structure inversion asymmetry in graphene.
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| 12. |
- Engelsen, Nils Johan, 1987, et al.
(författare)
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Ultrahigh-quality-factor micro- and nanomechanical resonators using dissipation dilution
- 2024
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Ingår i: Nature Nanotechnology. - 1748-3387 .- 1748-3395. ; 19:6, s. 725-737
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Forskningsöversikt (refereegranskat)abstract
- Mechanical resonators are widely used in sensors, transducers and optomechanical systems, where mechanical dissipation sets the ultimate limit to performance. Over the past 15 years, the quality factors in strained mechanical resonators have increased by four orders of magnitude, surpassing the previous state of the art achieved in bulk crystalline resonators at room temperature and liquid helium temperatures. In this Review, we describe how these advances were made by leveraging ‘dissipation dilution’—where dissipation is reduced through a combination of static tensile strain and geometric nonlinearity in dynamic strain. We then review the state of the art in strained nanomechanical resonators and discuss the potential for even higher quality factors in crystalline materials. Finally, we detail current and future applications of dissipation-diluted mechanical resonators.
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| 13. |
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| 14. |
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| 15. |
- Fadeel, B, et al.
(författare)
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Broaden the discussion
- 2013
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Ingår i: Nature nanotechnology. - : Springer Science and Business Media LLC. - 1748-3395 .- 1748-3387. ; 8:2, s. 71-71
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 16. |
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| 17. |
- Fatayer, Shadi, et al.
(författare)
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Reorganization energy upon charging a single molecule on an insulator measured by atomic force microscopy
- 2018
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Ingår i: Nature Nanotechnology. - : Springer Science and Business Media LLC. - 1748-3387 .- 1748-3395. ; 13:5, s. 376-380
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Tidskriftsartikel (refereegranskat)abstract
- Intermolecular single-electron transfer on electrically insulating films is a key process in molecular electronics 1-4 and an important example of a redox reaction 5,6 . Electron-transfer rates in molecular systems depend on a few fundamental parameters, such as interadsorbate distance, temperature and, in particular, the Marcus reorganization energy 7 . This crucial parameter is the energy gain that results from the distortion of the equilibrium nuclear geometry in the molecule and its environment on charging 8,9 . The substrate, especially ionic films 10 , can have an important influence on the reorganization energy 11,12 . Reorganization energies are measured in electrochemistry 13 as well as with optical 14,15 and photoemission spectroscopies 16,17 , but not at the single-molecule limit and nor on insulating surfaces. Atomic force microscopy (AFM), with single-charge sensitivity 18-22 , atomic-scale spatial resolution 20 and operable on insulating films, overcomes these challenges. Here, we investigate redox reactions of single naphthalocyanine (NPc) molecules on multilayered NaCl films. Employing the atomic force microscope as an ultralow current meter allows us to measure the differential conductance related to transitions between two charge states in both directions. Thereby, the reorganization energy of NPc on NaCl is determined as (0.8 ± 0.2) eV, and density functional theory (DFT) calculations provide the atomistic picture of the nuclear relaxations on charging. Our approach presents a route to perform tunnelling spectroscopy of single adsorbates on insulating substrates and provides insight into single-electron intermolecular transport.
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| 18. |
- Goswami, Sreetosh, et al.
(författare)
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Charge disproportionate molecular redox for discrete memristive and memcapacitive switching
- 2020
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Ingår i: Nature Nanotechnology. - : Springer Science and Business Media LLC. - 1748-3387 .- 1748-3395. ; 15:5, s. 380-389
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Tidskriftsartikel (refereegranskat)abstract
- Electronic symmetry breaking by charge disproportionation results in multifaceted changes in the electronic, magnetic and optical properties of a material, triggering ferroelectricity, metal/insulator transition and colossal magnetoresistance. Yet, charge disproportionation lacks technological relevance because it occurs only under specific physical conditions of high or low temperature or high pressure. Here we demonstrate a voltage-triggered charge disproportionation in thin molecular films of a metal-organic complex occurring in ambient conditions. This provides a technologically relevant molecular route for simultaneous realization of a ternary memristor and a binary memcapacitor, scalable down to a device area of 60 nm(2). Supported by mathematical modelling, our results establish that multiple memristive states can be functionally non-volatile, yet discrete-a combination perceived as theoretically prohibited. Our device could be used as a binary or ternary memristor, a binary memcapacitor or both concomitantly, and unlike the existing 'continuous state' memristors, its discrete states are optimal for high-density, ultra-low-energy digital computing. Charge disproportionation in thin molecular films of a metal-organic complex enables the realization of a ternary memristor and binary memcapacitor.
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| 19. |
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| 20. |
- Grommet, Angela Beth, 1991, et al.
(författare)
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Chemical Reactivity Under Nanoconfinement
- 2020
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Ingår i: Nature Nanotechnology. - : Springer Science and Business Media LLC. - 1748-3387 .- 1748-3395. ; 15:4, s. 256-271
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Forskningsöversikt (refereegranskat)
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