| 1. |
- Ferri, Julien, 1990, et al.
(author)
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Enhanced target normal sheath acceleration using colliding laser pulses
- 2019
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In: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 2
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Journal article (peer-reviewed)abstract
- Laser-solid interaction can lead to the acceleration of protons to tens of MeV. Here, we show that a strong enhancement of this acceleration can be achieved by splitting the laser pulse to two parts of equal energy and opposite incidence angles. Through the use of two- and three-dimensional Particle-In-Cell simulations, we find that the multi-pulse interaction leads to a standing wave pattern at the front side of the target, with an enhanced electric field and a substantial modification of the hot electron generation process. This in turn leads to significant improvement of the proton spectra, with an almost doubling of the accelerated proton energy and five-fold enhancement of the number of protons. The proposed scheme is robust with respect to incidence angles for the laser pulses, providing flexibility to the scheme, which should facilitate its experimental implementation.
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| 2. |
- Jünger, Christian, et al.
(author)
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Spectroscopy of the superconducting proximity effect in nanowires using integrated quantum dots
- 2019
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In: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 2:1
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Journal article (peer-reviewed)abstract
- The superconducting proximity effect has recently attracted a renewed interest as the basis of topologically nontrivial states in materials with a large spin–orbit interaction, with protected boundary states useful for quantum information technologies. However, spectroscopy of these states is challenging because of the limited control of conventional tunnel barriers. Here we report electronic spectroscopy measurements of the proximity gap in a semiconducting indium arsenide nanowire segment coupled to a superconductor, using quantum dots formed deterministically during the crystal growth. We extract characteristic parameters describing the proximity gap, which is suppressed for lower electron densities and fully developed for larger ones. This gate-tunable transition of the proximity effect can be understood as a transition from the long to the short junction regime of subgap bound states in the NW segment. Our device architecture opens up the way to systematic, quantitative spectroscopy studies of subgap states, such as Majorana-bound states.
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| 3. |
- Katcko, K., et al.
(author)
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Spin-driven electrical power generation at room temperature
- 2019
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In: Communications Physics. - : NATURE PUBLISHING GROUP. - 2399-3650. ; 2
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Journal article (peer-reviewed)abstract
- On-going research is exploring novel energy concepts ranging from classical to quantum thermodynamics. Ferromagnets carry substantial built-in energy due to ordered electron spins. Here, we propose to generate electrical power at room temperature by utilizing this magnetic energy to harvest thermal fluctuations on paramagnetic centers using spintronics. Our spin engine rectifies current fluctuations across the paramagnetic centers' spin states by utilizing so-called 'spinterfaces' with high spin polarization. Analytical and ab-initio theories suggest that experimental data at room temperature from a single MgO magnetic tunnel junction (MTJ) be linked to this spin engine. Device downscaling, other spintronic solutions to select a transport spin channel, and dual oxide/organic materials tracks to introduce paramagnetic centers into the tunnel barrier, widen opportunities for routine device reproduction. At present MgO MTJ densities in next-generation memories, this spin engine could lead to 'always-on' areal power densities that are highly competitive relative to other energy harvesting strategies.
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| 4. |
- Kuzmin, Leonid, 1946, et al.
(author)
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Photon-noise-limited cold-electron bolometer based on strong electron self-cooling for high-performance cosmology missions
- 2019
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In: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 2:1
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Journal article (peer-reviewed)abstract
- Bolometers for balloon and space missions have seen extensive development because of their capacity to test primordial conditions of the Universe. The major improvements consist in lowering the operating temperature to reach higher sensitivities. Here we show that an array of 192 cold-electron bolometers (CEB) demonstrates photon-noise-limited operation at the cryostat temperature of 310 mK due to effective self-cooling of the absorber. The direct electron cooling of nanoabsorber placed between normal metal - insulator - superconductor junctions has considerably higher efficiency than indirect cooling through massive suspended platform, that requires overcoming a weak electron-phonon conductance. The electron temperature reached 120 mK without a power load, and 225 mK with a 60 pW power load with self-noise of a single bolometer below 3⋅10-18WHz-1∕2 at a 0.01 pW power load. This bolometer works at electron temperature less than phonon temperature, thus being a good candidate for future space missions without the use of dilution refrigerators.
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| 5. |
- Liu, Lei, et al.
(author)
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Pressure-induced magnetovolume effect in CoCrFeAl high-entropy alloy
- 2019
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In: Communications Physics. - : NATURE PUBLISHING GROUP. - 2399-3650. ; 2
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Journal article (peer-reviewed)abstract
- High-entropy alloys (HEAs) composed of multiple-principal elements with (nearly) equimolar ratio establish a new conceptual framework for alloy design and hold a promise for extensive applications in industry, akin to the controlled expansion alloys (CEAs), such as Invar alloys. Spontaneously, one question emerges - would it be possible to synthesize a novel class of alloys combining the virtues of both CEAs and HEAs? Here, we report the pressure-induced magnetovolume effect in the body-centered-cubic CoCrFeAl HEA coupled with magnetic phase transitions from ferromagnetic to paramagnetic, and to non-magnetic states, originating from the successive collapses of local magnetic moments of Co and Fe. The observed magnetovolume anomalies, occurring in a progressive way, tailor appreciably the coefficient of thermal expansion of CoCrFeAl. These results further strengthen HEAs' anticipated potential for designing multifunctional materials in virtue of their multiple outstanding properties, and reveal possible routes for their future synthesis.
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| 6. |
- Ovesen, Simon, 1993, et al.
(author)
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Interlayer exciton dynamics in van der Waals heterostructures
- 2019
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In: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 2:1
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Journal article (peer-reviewed)abstract
- Atomically thin transition metal dichalcogenides can be stacked to van der Waals heterostructures enabling the design of new materials with tailored properties. The strong Coulomb interaction gives rise to interlayer excitons, where electrons and holes are spatially separated in different layers. In this work, we reveal the time- and momentum-dependent elementary processes behind the formation, thermalization and photoemission of interlayer excitons for the exemplary MoSe2-WSe2 heterostructure. We identify tunneling of holes from MoSe2 to WSe2 on a ps timescale as the crucial process for interlayer exciton formation. We also predict a drastic reduction of the formation time as a function of the interlayer energy offset suggesting that interlayer excitons can be externally tuned. Finally, we explain the experimental observation of a dominant photoluminescence from interlayer excitons despite the vanishingly small oscillator strength as a consequence of huge interlayer exciton occupations at low temperatures.
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