| 1. |
- Melgaard, Michael
(författare)
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Quantum collisions in semi-constrained structures
- 2007
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Ingår i: Modern physics letters B. - 0217-9849. ; 21:13, s. 767-779
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Tidskriftsartikel (refereegranskat)abstract
- The problem of a quantum particle moving in a narrow, bent two-dimensional channel is used to illustrate features of collisions in systems with semi-constrained structures. The collision theory of such systems is developed and, under certain general restrictions on the geometry, the following properties are rigorously established: (1) The (localized) Moller wave operator exist and the S operator is unitary in the scattering channels. (2) The singular spectrum is discrete in intervals away from the continuum thresholds. The discussion is based on a time-dependent approach.
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| 2. |
- Shen, Jian Qi
(författare)
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Isotropic negatively-refracting atomic-vapor medium
- 2007
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Ingår i: Modern physics letters B. - 0217-9849. ; 21:12, s. 717-728
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Tidskriftsartikel (refereegranskat)abstract
- A new scenario to realize negative refraction with a photonic-resonant vapor material that can exhibit both electric and magnetic responses via multilevel quantum coherence is suggested. Compared with the previous method of artificial composite metamaterial, where the mechanism was considered by means of classical electromagnetic theory and the materials produced have anisotropic millimetre-scale composite structures, the present scheme suggested within the framework of quantum optics can be used to design and fabricate isotropic negatively-refracting materials with atomic-scale microscopic structure units. Such an advantage may lead to a potentially important application in the techniques of superlens and perfect imaging.
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| 3. |
- Sun, Jie, et al.
(författare)
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Scanning electron microscopy observation of in-device InAs/AlAs quantum dots by selective etching of capping layers
- 2007
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Ingår i: Modern Physics Letters B. - 0217-9849. ; 21:14, s. 859-866
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Tidskriftsartikel (refereegranskat)abstract
- Self-assembled InAs/AlAs quantum dots embedded in a resonant tunneling diode device structure are grown by molecular beam epitaxy. Through the selective etching in a C6H8O7 center dot H2O-K3C6H5O7 center dot H2O-H2O2 buffer solution, 310 nm GaAs capping layers are removed and the InAs/AlAs quantum dots are observed by field-emission scanning electron microscopy. It is shown that as-fabricated quantum dots have a diameter of several tens of nanometers and a density of 10(10) cm(-2) order. The images taken by this means are comparable or slightly better than those of transmission electron microscopy. The undercut of the InAs/AlAs layer near the edges of mesas is detected and that verifies the reliability of the quantum dot images. The inhomogeneous oxidation of the upper AlAs barrier in H2O2 is also observed. By comparing the morphologies of the mesa edge adjacent regions and the rest areas of the sample, it is concluded that the physicochemical reaction introduced in this letter is diffusion limited.
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