Phase transition and charge transport through a triple dot device beyond the Kondo regime

Semiconductor quantum dot structure provides a promising basis for quantum information processing, within which to reveal the quantum phase and charge transport is one of the most important issues. In this paper, by means of the numerical renormalization group technique, we study the quantum phase transition and the charge transport for a parallel triple dot device in the strongly correlated limit, focusing on the effect of inter-dot hopping t beyond the Kondo regime. We find the quantum behaviors depend closely on the initial electron number on the dots, and the present model may map to single,double, and side-coupled impurity models in different parameter spaces. An orbital spin-1/2 Kondo effect between the conduction leads and the bonding orbital, and several magnetic-frustration phases are demonstrated when t is adjusted to different regimes. To understand these phenomena, a canonical transformation of the energy levels is given, and important physical quantities with respect to increasing t and necessary theoretical discussions are shown.

Synergistic enhancement of spin-phonon interaction in a hybrid system

An investigation to significantly enhance coupling to nitrogen-vacancy(NV)centers at a single-quanta level is of great interest to further explore its applications in quantum information processing(QIP).This study explores a joint scheme to further enhance NV-phonon coherent coupling with two methods working together in hybrid optomechanical systems.Both methods are mechanics-induced mode field coupling(MFC)that lead,respectively,to the modification of the spatial distribution of the optical field and the mechanical parametric amplification(MPA)realized by modulating the mechanical spring constant in time.With the joint assistance of MFC and MPA,the coherent coupling between the NV spin and one supermode of the mechanical resonators(MRs)can be further significantly enhanced with the rate∝n_(cav)e^(r).Several potential applications are also discussed in this work.With the ultimate goal to enhance the coupling to NV spin at a single-quanta level,this attempt may provide a promising spin-phonon platform to implement more active control.