Institution
Solid State Physics Laboratory
Facility•Delhi, India•
About: Solid State Physics Laboratory is a facility organization based out in Delhi, India. It is known for research contribution in the topics: Quantum dot & Dielectric. The organization has 1754 authors who have published 2597 publications receiving 50601 citations.
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TL;DR: In this paper, the role of nine different scattering mechanisms (ionized impurity, polar and non-polar optical, acoustic, dislocation, strain field, alloy disorder, neutral impurity and piezoelectric) in limiting hole mobilities in p-type Hg1−xCdxTe crystals was analyzed.
Abstract: In this paper, we analyze and discuss the roles of nine different scattering mechanisms—ionized impurity, polar and nonpolar optical, acoustic, dislocation, strain field, alloy disorder, neutral impurity, and piezoelectric—in limiting the hole mobilities in p-type Hg1−xCdxTe crystals. The analysis is based on obtaining a good fit between theory and experiment for the light and heavy hole drift mobilities by optimizing certain unknown (or at the most vaguely known) material parameters such as the heavy hole mobility effective mass, degree of compensation, and the dislocation and strain field scattering strengths. For theoretical calculations, we have adopted the relaxation time approach, keeping in view its inadequacy for the polar scattering. The energy dispersive hole relaxation times have been drawn from the published literature that take into account the p-symmetry of valence band wave functions. The temperature dependencies of multiple charge states of impurities and of Debye screening length have been taken into account through a numerical calculation for the Fermi energy. Mobility data for the present analysis have been selected from the HgCdTe literature to represent a wide range of material characteristics (x=0.2–0.4, p=3×1015–1×1017 cm−3 at 77K, μpeak≅200-1000cm2V−1s−1). While analyzing the light hole mobility, the acoustic deformation and neutral impurity potentials were also treated as adjustable. We conclude that
• the heavy hole mobility is largely governed by the ionized impurity scattering, unless the strain field or dislocation scattering below 50K, or the polar scattering above 200K, become dominant;
• the light hole mobility is mainly governed by the acoustic phonon scattering, except at temperatures below 30K where the neutral impurity, strain field and dislocation scattering also become significant;
• the intervalence scattering transitions make negligible impact on the heavy hole mobility, but virtually limit the light hole mobility;
• the alloy disorder scattering does not dominate in any temperature region, although it exercises some influence at intermediate temperatures;
• the heavy hole mobility effective mass ratio mhh/mo∼-0.28–0.33 for crystals with x<0.4; and
• the light hole band deformation potential constant is ∼12 eV.
23 citations
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TL;DR: In this paper, a coherent spin shuttle through a GaAs/AlGaAs quadruple-quantum-dot array was demonstrated, starting with two electrons in a spin-singlet state in the first dot, one electron over to either the second, third or fourth dot.
Abstract: We demonstrate a coherent spin shuttle through a GaAs/AlGaAs quadruple-quantum-dot array. Starting with two electrons in a spin-singlet state in the first dot, we shuttle one electron over to either the second, third or fourth dot. We observe that the separated spin-singlet evolves periodically into the $m=0$ spin-triplet and back before it dephases due to nuclear spin noise. We attribute the time evolution to differences in the local Zeeman splitting between the respective dots. With the help of numerical simulations, we analyse and discuss the visibility of the singlet-triplet oscillations and connect it to the requirements for coherent spin shuttling in terms of the inter-dot tunnel coupling strength and rise time of the pulses. The distribution of entangled spin pairs through tunnel coupled structures may be of great utility for connecting distant qubit registers on a chip.
23 citations
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TL;DR: In this paper, an algorithm based on DUT S parameters was developed to extract the electrical parameters of the equivalent circuit up to 18 GHz for a large number of resistors of varying geometries and geometry-scaleable curve-fitted equations for the model parameters have been obtained.
Abstract: The lumped-element electrical equivalent circuit of nichrome (NiCr) resistors is important for monolithic microwave integrated circuit (MMIC) design. This paper presents a methodology for the RF parameter extraction of thin-film NiCr resistors fabricated on GaAs substrate. An algorithm based on DUT S parameters has been developed to extract the electrical parameters of the equivalent circuit up to 18 GHz for a large number of resistors of varying geometries and geometry-scaleable curve-fitted equations for the model parameters have been obtained. The computed S parameters, based on the extracted model parameters, agree reasonably well with the measured S parameters. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 409–412, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11233
23 citations
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TL;DR: In this paper, the authors reported acceleration measurements using a detector adapted from high-energy physics to track particles in a laboratory water flow at Reynolds numbers up to 63,000 and found that universal K41 scaling of the acceleration variance is attained at high Reynolds numbers.
Abstract: The motion of fluid particles as they are pushed along erratic trajectories by fluctuating pressure gradients is fundamental to transport and mixing in turbulence. It is essential in cloud formation and atmospheric transport, processes in stirred chemical reactors and combustion systems, and in the industrial production of nanoparticles. The perspective of particle trajectories has been used successfully to describe mixing and transport in turbulence, but issues of fundamental importance remain unresolved. One such issue is the Heisenberg-Yaglom prediction of fluid particle accelerations, based on the 1941 scaling theory of Kolmogorov (K41). Here we report acceleration measurements using a detector adapted from high-energy physics to track particles in a laboratory water flow at Reynolds numbers up to 63,000. We find that universal K41 scaling of the acceleration variance is attained at high Reynolds numbers. Our data show strong intermittency---particles are observed with accelerations of up to 1,500 times the acceleration of gravity (40 times the root mean square value). Finally, we find that accelerations manifest the anisotropy of the large scale flow at all Reynolds numbers studied.
23 citations
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TL;DR: In this paper, a quantum dot has been etched in bilayer graphene connected by two small constrictions to the leads, and the authors show that this structure does not behave like a single quantum dot but consists of at least three sites of localized charge in series.
Abstract: A quantum dot has been etched in bilayer graphene connected by two small constrictions to the leads. We show that this structure does not behave like a single quantum dot but consists of at least three sites of localized charge in series. The high symmetry and electrical stability of the device allowed us to triangulate the positions of the different sites of localized charge and find that one site is located in the island and one in each of the constrictions. Nevertheless we measure many consecutive non-overlapping Coulomb-diamonds in series. In order to describe these findings, we treat the system as a strongly coupled serial triple quantum dot. We find that the non-overlapping Coulomb diamonds arise due to higher order cotunneling through the outer dots located in the constrictions. We extract all relevant capacitances, simulate the measured data with a capacitance model and discuss its implications on electrical transport.
23 citations
Authors
Showing all 1757 results
Name | H-index | Papers | Citations |
---|---|---|---|
Alain Dufresne | 111 | 358 | 45904 |
Yang Ren | 79 | 880 | 26341 |
Klaus Ensslin | 70 | 638 | 21385 |
Werner Wegscheider | 69 | 933 | 21984 |
Takashi Takahashi | 65 | 424 | 14234 |
Liu Hao Tjeng | 64 | 322 | 13752 |
Nicholas E. Geacintov | 63 | 453 | 15636 |
Manfred Sigrist | 61 | 468 | 18362 |
Thomas Ihn | 61 | 475 | 14159 |
Takafumi Sato | 59 | 263 | 11032 |
Christoph Stampfer | 59 | 315 | 14422 |
Christian Colliex | 58 | 289 | 14618 |
Takashi Mizokawa | 57 | 400 | 11697 |
Eberhard Bodenschatz | 57 | 374 | 13208 |
Bertram Batlogg | 55 | 190 | 9459 |