Тип публикации: глава из книги
Год издания: 2008
Аннотация: We consider open quantum dots (QD) whose spectra can be varied continuously by variation of gate voltage. We show that bound states in the continuum (BICs) may occur for discrete values of the voltage and energy of incident electrons. They are localized inside the QD and superposed by the transport solution. However superposition cПоказать полностьюoefficient depends on the way the BIC point is approached. For integrable QD this phenomenon occurs, if the QD spectrum is degenerated incidentally. However a BIC might occur for irregular shape of QD. Both types of QDs are considered analytically in the simplest case of a two level QD and are complemented by numerical calculations for the realistic QB. Although each eigen state of QD is coupled to waveguide, the coupling of BIC with propagating mode of the waveguide turns to zero because of interference with other resonances. As a result, resonance width tends to zero for approaching to the BIC point. In order to find explicitly BICs we are looking for the complex eigenvalues of the effective non hermitian Hamiltonian which respond for positions and widths of the resonance states. In particular we show that BIC is an eigenstate of the effective Hamiltonian with real eigenvalue. We present a few numerical examples of BICs in realistic QDs and in systems of double QDs coupled by a wire with variable spectrum. In the framework of the impurity Anderson model we took into account Coulomb effects. Such an approach allows one to find the Green function of the closed QD exactly. Further, the solution of the Dyson equation for full Green function describes the open QD.We show that the Coulomb repulsion does not eliminate the BIC, but on the contrary, replicates BICs as two-electron BICs. © 2008 by Nova Science Publishers, Inc. All rights reserved.
Журнал: QUANTUM DOTS: RESEARCH, TECHNOLOGY AND APPLICATIONS
Номера страниц: 545-575