Spin dynamics and magneto-optical response in charge-neutral tunnel-coupled quantum dots

Abstract

We model the electron and hole spin dynamics in an undoped double quantum dot structure, considering the carrier tunneling between quantum dots. Taking into account also the presence of an in-plane or tilted magnetic field, we provide the simulation of magneto-optical experiments, like the time resolved Kerr rotation measurement, which are performed currently on such structures to probe the temporal spin dynamics. With our model, we reproduce the experimentally observed effect of the extension of the spin polarization life time caused by the spatial charge separation, which may occur in structures of this type. Moreover, we provide a number of qualitative predictions concerning the necessary conditions for observation of this effect as well as about possible channels of its suppression, including the spin-orbit coupling, which leads to tunneling of carriers accompanied by a spin-flip. We consider also the impact of the magnetic field tilting, which results in an interesting spin polarization dynamics.

Tunneling-related electron spin relaxation in self-assembled quantum-dot molecules

“…Apart from the total rate, we show also the contribution due to various couplings calculated by disabling all the respective matrix elements in the Hamiltonian but the one in question. One may notice that all the rates are non-vanishing at B → 0, with the pronounced domination of the Desselhus spin-orbit interaction in a wide range of fields up to B = ∼15 T. Via fitting with aB m +c, we find an exponent of m = 2 which, along with the order of magnitude of Γ ↑↓ , is in agreement with the recent perturbative calculation concerning this channel 31 . At higher fields, the Dresselhaus contribution is surpassed by those arising from shear-strain-induced couplings between the conduction and valence bands and among the latter (dashed and dotted lines, respectively), which are those mechanisms that were found to dominate in the case of relaxation in the Zeeman doublet 50 .…”

“…Regarding phonon-assisted tunneling in quantum-dot molecules, although the physics of the orbital transition itself has been widely recognized [23][24][25][26][27][28] , studies concerning the behavior of spin states during tunneling are scarce. Those focus mostly on phonon induced spin pure dephasing during tunneling 29,30 with a single * Electronic address: michal.gawelczyk@pwr.edu.pl work containing a perturbative estimation of the rate of spin-orbit-induced spin-flip tunneling 31 .…”

Strongly temperature-dependent recombination kinetics of a negatively charged exciton in asymmetric quantum dots at 1.55 µm

“…Dashed arrows in Fig. 4 mark the processes of electron orbital relaxation accompanied by a spin flip, 38,39 while the dotted arrows depict transitions that involve electron spin flip without orbital relaxation. 40,41 We are able to obtain a qualitative agreement with the experimental temperature dependence of X − lifetimes assuming 1/Γ ≥ 1 µs for both spin-flip-assisted relaxation processes and very efficient spin flips, 1/Γ = 5 ns.…”

InAs on InP Quantum Dashes as Single Photon Emitters at the Second Telecommunication Window: Optical, Kinetic, and Excitonic Properties

“…Considering the almost equal intensities of X D and XX D transitions in our case, we could have some indications on spin-flip coupling of bright and dark exciton states, which induces a transition from dark to bright and is mediated by spin-orbit interactions and acoustic phonons due to the higher lateral extension of the QDash than for e.g. InAs QDs [19][20][21]. This is however unclear yet and needs further investigation.…”