| 1. |
- Brotons-Gisbert, Mauro, et al.
(författare)
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Coulomb blockade in an atomically thin quantum dot coupled to a tunable Fermi reservoir
- 2019
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Ingår i: Nature Nanotechnology. - : NATURE PUBLISHING GROUP. - 1748-3387 .- 1748-3395. ; 14:5, s. 442-446
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Tidskriftsartikel (refereegranskat)abstract
- Gate-tunable quantum-mechanical tunnelling of particles between a quantum confined state and a nearby Fermi reservoir of delocalized states has underpinned many advances in spintronics and solid-state quantum optics. The prototypical example is a semiconductor quantum dot separated from a gated contact by a tunnel barrier. This enables Coulomb blockade, the phenomenon whereby electrons or holes can be loaded one-by-one into a quantum dot(1,2). Depending on the tunnel-coupling strength(3,4), this capability facilitates single spin quantum bits(1,2,5) or coherent many-body interactions between the confined spin and the Fermi reservoirs(6,7). Van der Waals (vdW) heterostructures, in which a wide range of unique atomic layers can easily be combined, offer novel prospects to engineer coherent quantum confined spins(8,9), tunnel barriers down to the atomic limit(10) or a Fermi reservoir beyond the conventional flat density of states(11). However, gate-control of vdW nanostructuresu(12-16) at the single particle level is needed to unlock their potential. Here we report Coulomb blockade in a vdW heterostructure consisting of a transition metal dichalcogenide quantum dot coupled to a graphene contact through an atomically thin hexagonal boron nitride (hBN) tunnel barrier. Thanks to a tunable Fermi reservoir, we can deterministically load either a single electron or a single hole into the quantum dot. We observe hybrid excitons, composed of localized quantum dot states and delocalized continuum states, arising from ultra-strong spin-conserving tunnel coupling through the atomically thin tunnel barrier. Probing the charged excitons in applied magnetic fields, we observe large gyromagnetic ratios (similar to 8). Our results establish a foundation for engineering next-generation devices to investigate either novel regimes of Kondo physics or isolated quantum bits in a vdW heterostructure platform.
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| 2. |
- Carlmark, Anna, 1974-
(författare)
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A polymeric coat for nanodroplets
- 2019
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Ingår i: Nature Nanotechnology. - : Nature Publishing Group. - 1748-3387 .- 1748-3395. ; 14, s. 640-641
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Grafting nanodroplets by surface-initiated atom transfer radical polymerization can be carried out at liquid–liquid interfaces.
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| 3. |
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| 4. |
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| 5. |
- 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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| 6. |
- Güttinger, J., et al.
(författare)
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Energy-dependent path of dissipation in nanomechanical resonators
- 2017
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Ingår i: Nature Nanotechnology. - : Springer Science and Business Media LLC. - 1748-3387 .- 1748-3395. ; 12:7, s. 631-636
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Tidskriftsartikel (refereegranskat)abstract
- Energy decay plays a central role in a wide range of phenomena, such as optical emission, nuclear fission, and dissipation in quantum systems. Energy decay is usually described as a system leaking energy irreversibly into an environmental bath. Here, we report on energy decay measurements in nanomechanical systems based on multilayer graphene that cannot be explained by the paradigm of a system directly coupled to a bath. As the energy of a vibrational mode freely decays, the rate of energy decay changes abruptly to a lower value. This finding can be explained by a model where the measured mode hybridizes with other modes of the resonator at high energy. Below a threshold energy, modes are decoupled, resulting in comparatively low decay rates and giant quality factors exceeding 1 million. Our work opens up new possibilities to manipulate vibrational states, engineer hybrid states with mechanical modes at completely different frequencies, and to study the collective motion of this highly tunable system.
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| 7. |
- Hou, Lili, et al.
(författare)
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Optically switchable organic light-emitting transistors
- 2019
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Ingår i: Nature Nanotechnology. - : Springer Science and Business Media LLC. - 1748-3387 .- 1748-3395. ; 14:4, s. 347-353
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Tidskriftsartikel (refereegranskat)abstract
- Organic light-emitting transistors are pivotal components for emerging opto- and nanoelectronics applications, such as logic circuitries and smart displays. Within this technology sector, the integration of multiple functionalities in a single electronic device remains the key challenge. Here we show optically switchable organic light-emitting transistors fabricated through a judicious combination of light-emitting semiconductors and photochromic molecules. Irradiation of the solution-processed films at selected wavelengths enables the efficient and reversible tuning of charge transport and electroluminescence simultaneously, with a high degree of modulation (on/off ratios up to 500) in the three primary colours. Different emitting patterns can be written and erased through a non-invasive and mask-free process, on a length scale of a few micrometres in a single device, thereby rendering this technology potentially promising for optically gated highly integrated full-colour displays and active optical memory.
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| 8. |
- Houshang, Afshin, et al.
(författare)
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Spin-wave-beam driven synchronization of nanocontact spin-torque oscillators
- 2016
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Ingår i: Nature Nanotechnology. - 1748-3387 .- 1748-3395. ; 11, s. 280-286
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Tidskriftsartikel (refereegranskat)abstract
- The synchronization of multiple nanocontact spin-torque oscillators (NC-STOs) is mediated by propagating spin waves (SWs). Although it has been shown that the Oersted field generated in the vicinity of the NC can dramatically alter the emission pattern of SWs, its role in the synchronization behaviour of multiple NCs has not been considered so far. Here we investigate the synchronization behaviour in multiple NC-STOs oriented either vertically or horizontally, with respect to the in-plane component of the external field. Synchronization is promoted (impeded) by the Oersted field landscape when the NCs are oriented vertically (horizontally) due to the highly anisotropic SW propagation. Not only is robust synchronization between two oscillators observed for separations larger than 1,000nm, but synchronization of up to five oscillators, a new record, has been observed in the vertical array geometry. Furthermore, the synchronization can no longer be considered mutual in nature.
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| 9. |
- Josefsson, Martin, et al.
(författare)
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A quantum-dot heat engine operating close to the thermodynamic efficiency limits
- 2018
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Ingår i: Nature Nanotechnology. - : Springer Science and Business Media LLC. - 1748-3387 .- 1748-3395. ; 13:10, s. 920-924
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Tidskriftsartikel (refereegranskat)abstract
- Cyclical heat engines are a paradigm of classical thermodynamics, but are impractical for miniaturization because they rely on moving parts. A more recent concept is particle-exchange (PE) heat engines, which uses energy filtering to control a thermally driven particle flow between two heat reservoirs1,2. As they do not require moving parts and can be realized in solid-state materials, they are suitable for low-power applications and miniaturization. It was predicted that PE engines could reach the same thermodynamically ideal efficiency limits as those accessible to cyclical engines3–6, but this prediction has not been verified experimentally. Here, we demonstrate a PE heat engine based on a quantum dot (QD) embedded into a semiconductor nanowire. We directly measure the engine’s steady-state electric power output and combine it with the calculated electronic heat flow to determine the electronic efficiency η. We find that at the maximum power conditions, η is in agreement with the Curzon–Ahlborn efficiency6–9 and that the overall maximum η is in excess of 70% of the Carnot efficiency while maintaining a finite power output. Our results demonstrate that thermoelectric power conversion can, in principle, be achieved close to the thermodynamic limits, with direct relevance for future hot-carrier photovoltaics10, on-chip coolers or energy harvesters for quantum technologies.
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| 10. |
- Kapaklis, Vassilios, 1978-
(författare)
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Magnetizing semiconductors with light
- 2018
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Ingår i: Nature Nanotechnology. - : Springer Science and Business Media LLC. - 1748-3387 .- 1748-3395. ; 13:6, s. 438-439
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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