排序方式: 共有53条查询结果,搜索用时 125 毫秒
41.
Meunier T Vink IT van Beveren LH Tielrooij KJ Hanson R Koppens FH Tranitz HP Wegscheider W Kouwenhoven LP Vandersypen LM 《Physical review letters》2007,98(12):126601
We observe an experimental signature of the role of phonons in spin relaxation between triplet and singlet states in a two-electron quantum dot. Using both the external magnetic field and the electrostatic confinement potential, we change the singlet-triplet energy splitting from 1.3 meV to zero and observe that the spin relaxation time depends nonmonotonously on the energy splitting. A simple theoretical model is derived to capture the underlying physical mechanism. The present experiment confirms that spin-flip energy is dissipated in the phonon bath. 相似文献
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Michael J. Doyle Arjan P. Kouwenhoven Cornelis A. Schaap Bart van Oort 《Journal of organometallic chemistry》1979,174(3):C55-C58
Solutions of dodecacarbonyl-triangulo-triruthenium [Ru3(CO)12] have been shown to be catalyst precursors for the Fischer-Tropsch reaction; the catalyst formed under the reaction conditions is heterogeneous; no indication of homogeneous activity was found. 相似文献
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3,4 - Di(methoxycarbonyl) - 5 - pyrrolidinobenzo[b]thiepin 5 is synthesized by a [2+2]cycloaddition of 3 - pyrrolidinobenzo[b]thiephene 3 to dimethyl acetylenedicarboxylate, with subsequent ring opening of the cyclobutene moiety in the intermediate 6,7-di(methoxycarbonyl)-5-pyrrolidino - 2 - thiabenzo[b]bicyclo[3.2.0]hepta - 3,6 - diene 4 (detectable by PMR spectroscopy at ?30°C). Hydrolysis of the pyrrolidino group in 5 affords 3,4 - di(methoxycarbonyl) - 5 - hydroxybenzo[b]thiepin 8. Peracid oxidation of 5 yields the corresponding 1,1-dioxide. The benzo[b]thiepins are thermally unstable and (depending on the substituents) either extrude sulphur or rearrange to a 4-mercapto-1-naphthol, probably via the thianorcaradiene as the intermediate. The kinetics of the latter reaction are discussed. On being irradiated, the benzo[b]thiepins isomerize to 2-thiabenzo[b]bicyclo[3.2.0]hepta-3,6-dienes. 相似文献
44.
Shell Filling and Spin Effects in a Few Electron Quantum Dot 总被引:1,自引:0,他引:1
Tarucha S Austing DG Honda T van der Hage RJ Kouwenhoven LP 《Physical review letters》1996,77(17):3613-3616
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van der Wiel WG De Franceschi S Elzerman JM Tarucha S Kouwenhoven LP Motohisa J Nakajima F Fukui T 《Physical review letters》2002,88(12):126803
We report a strong Kondo effect (Kondo temperature approximately 4 K) at high magnetic field in a selective area growth semiconductor quantum dot. The Kondo effect is ascribed to a singlet-triplet transition in the ground state of the dot. At the transition, the low-temperature conductance approaches the unitary limit. Away from the transition, for low bias voltages and temperatures, the conductance is sharply reduced. The observed behavior is compared to predictions for a two-stage Kondo effect in quantum dots coupled to single-channel leads. 相似文献
48.
L. P. Kouwenhoven N. C. van der Vaart A. T. Johnson W. Kool C. J. P. M. Harmans J. G. Williamson A. A. M. Staring C. T. Foxon 《Zeitschrift für Physik B Condensed Matter》1991,85(3):367-373
We have studied charging effects in a lateral split-gate quantum dot defined by metal gates in the two dimensional electron gas (2 DEG) of a GaAs/AlGaAs heterostructure. The gate structure allows an independent control of the conductances of the two tunnel barriers separating the quantum dot from the two 2 DEG leads, and enables us to vary the number of electrons that are localized in the dot. We have measured Coulomb oscillations in the conductance and the Coulomb staircase in current-voltage characteristics and studied their dependence on the conductances of the tunnel barriers. We show experimentally that at zero magnetic field charging effects start to affect the transport properties when both barrier conductances are smaller than the first quantized conductance value of a point contact at 2e
2/h. The experiments are described by a simple model in terms of electrochemical potentials, which includes both the discreteness of the electron charge and the quantum energy states due to confinement. 相似文献
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Engel HA Golovach VN Loss D Vandersypen LM Elzerman JM Hanson R Kouwenhoven LP 《Physical review letters》2004,93(10):106804
We consider electron spin qubits in quantum dots and define a measurement efficiency e to characterize reliable measurements via n-shot readouts. We propose various implementations based on a double dot and a quantum point contact (QPC) and show that the associated efficiencies e vary between 50% and 100%, allowing single-shot readout in the latter case. We model the readout microscopically and derive its time dynamics in terms of a generalized master equation, calculate the QPC current, and show that it allows spin readout under realistic conditions. 相似文献