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Field Squeezing in a Quantum-Dot Molecule Jaynes-Cummings Model
摘要： We investigate the field squeezing in a system composed of an initial coherent field interacting with two quantum dots coupled by electron tunneling. An approximate quantum-dot molecule Jaynes-Cummings model describing the system is given, and the effects of physical quantities, such as the temperature, phonon-electron interaction, mean photon number, field detuning, and tunneling-level detuning, are discussed in detail.
关键词： Jaynes-Cummings model,phonon-electron interaction,electron tunneling,quantum-dot molecule,field squeezing
更新于2025-09-23 15:19:57
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Quantum dot molecule formation in Si-Ge heteroepitaxy on pita??patterned Si(001) substrate : A theoretical study
摘要： Quantum dot molecules refer to nanostructures consisting of four quantum dots around a central pit. These are observed to form in Si-Ge heteroepitaxy and are considered an alternative to quantum dots for strain relaxation. Here we use numerical simulations of a continuum model of strained heteroepitaxy to show the spontaneous formation of quantum dot molecules in thick Si0:5Ge0:5 films grown on pit–patterned Si substrates. The route to their formation first involves a quantum dot in the pit, followed by removal of material from the pit to form quantum dot molecules. These molecules are formed for smaller pit widths, whereas larger pit widths tend to create a ridged surface. A mature single–walled quantum dot molecule has a typical size of about 220 nm. On reducing the wavelength of the original pit–pattern, we notice that multiple–walled quantum dot molecules form, due to the interactions with other nearby molecules. Our results broadly agree with experiment and suggest that QDM formation on patterned substrates does not necessarily have a nucleation barrier and can take place following the usual evolution of the Asaro–Tiller–Grinfeld instability.
关键词： Heteroepitaxy,Quantum Dot Molecule,Patterned substrate
更新于2025-09-16 10:30:52
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Scenarios of local spectral property and multifunctional spin selecting for a triple quantum dot molecule: How do the bonding and antibonding orbitals contribute to the spin currents?
摘要： Molecular electronic device is considered as a promising candidate for next generation electronic component, where the basic challenge involves understanding the charge and spin transports through molecular objects. In this paper, with the help of the sophisticated numerical renormalization group technique, we study theoretically the spin selective transport in a parallel triple quantum dot molecular device pierced by a local magnetic field along z axis. Based on simplified parameters of real molecular system, we find such device acts as a multi-functional spin selector when the inter-molecule tunneling couplings are asymmetric, including two 100% polarized spin-up summits, and one 100% spin-down summit in the linear conductance. We show in detail the local density of states for the bonding and anti-boding orbitals, and attribute the spin selection to the orbital polarized Coulomb blockade effect. We demonstrate our numerical results are consistent with those estimated by the analytical techniques, including the Friedel sum rule and the energy level crossings of the isolated orbitals.
关键词： Coulomb blockade effect,Multifunctional spin selector,Triple quantum dot molecule,Numerical renormalization group technique,Molecular electronics device
更新于2025-09-12 10:27:22