| 1. |
- Ahmed, Hamad, et al.
(författare)
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Experimental Observation of Thin-shell Instability in a Collisionless Plasma
- 2017
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Ingår i: Astrophysical Journal Letters. - : Institute of Physics Publishing (IOPP). - 2041-8205 .- 2041-8213. ; 834:2
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Tidskriftsartikel (refereegranskat)abstract
- We report on the experimental observation of the instability of a plasma shell, which formed during the expansion of a laser-ablated plasma into a rarefied ambient medium. By means of a proton radiography technique, the evolution of the instability is temporally and spatially resolved on a timescale much shorter than the hydrodynamic one. The density of the thin shell exceeds that of the surrounding plasma, which lets electrons diffuse outward. An ambipolar electric field grows on both sides of the thin shell that is antiparallel to the density gradient. Ripples in the thin shell result in a spatially varying balance between the thermal pressure force mediated by this field and the ram pressure force that is exerted on it by the inflowing plasma. This mismatch amplifies the ripples by the same mechanism that drives the hydrodynamic nonlinear thin-shell instability (NTSI). Our results thus constitute the first experimental verification that the NTSI can develop in colliding flows.
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| 2. |
- Hugger, S, et al.
(författare)
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Magnetic-barrier-induced conductance fluctuations in quantum wires
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 78:16, s. 165307-
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Tidskriftsartikel (refereegranskat)abstract
- Quasiballistic semiconductor quantum wires are exposed to localized perpendicular magnetic fields, also known as magnetic barriers. Pronounced, reproducible conductance fluctuations as a function of the magnetic barrier amplitude are observed. The fluctuations are strongly temperature dependent and remain visible up to temperatures of approximate to 10 K. Simulations based on recursive Greens functions suggest that the conductance fluctuations originate from parametric interferences of the electronic wave functions, which experience scattering between the magnetic barrier and the electrostatic potential landscape.
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| 3. |
- Tarasov, A, et al.
(författare)
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Quantized Magnetic Confinement in Quantum Wires
- 2010
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Ingår i: PHYSICAL REVIEW LETTERS. - : American Physical Society. - 0031-9007. ; 104:18, s. 186801-
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Tidskriftsartikel (refereegranskat)abstract
- Ballistic quantum wires are exposed to longitudinal profiles of perpendicular magnetic fields composed of a spike and a homogeneous part. An asymmetric magnetoconductance peak as a function of the homogeneous magnetic field is found, comprising quantized conductance steps in the interval where the homogeneous magnetic field and the magnetic barrier have identical polarities, and a characteristic shoulder with several resonances in the interval of opposite polarities. The observations are interpreted in terms of inhomogeneous diamagnetic shifts of the quantum wire modes leading to magnetic confinement.
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