InAs量子点中自旋-轨道相互作用下电子自旋弛豫的参量特征

本文在处理InAs单电子量子点哈密顿模型时,将自旋-轨道(SO)相互作用作为微扰项,计算在Fock-Darwin本征函数下SO相互作用的矩阵元,利用其对能级和波函数的二阶修正,并且考虑新的能级对g因子和有效质量m^*的影响,计算得到在声子协助下电子的自旋弛豫率Γ的表达式.给出了InAs量子点中声子协助的电子自旋弛豫率Γ对于限制势频率ω₀、温度T、纵向高度z_{0关键词： 自旋弛豫率 自旋-轨道(SO)相互作用 InAs量子点 Fock-Darwin本征函数}

Parametric properties of the electron spin relaxation due to spin-orbit interaction in InAs quantum dots

To deal with the Hamiltonian model in InAs QDs with a single electron, we’ve taken the SO interaction as a perturbation term, calculated the SO matrix elements under Fock-Darwin eigenfunction which are used for second order corrections on the energies and wave functions, and considered the influence of new energy levels on g factor and effective mass m^*. The expression of phonon-assisted electron spin relaxation rate Γ in InAs QDs is deduced, which shows different dependences on confined potential frequency ω₀, temperature T, vertical height z₀ and magnetic field B. Among them, temperature for the electron spin relaxation plays a dominant role, followed by lateral confinement potential frequency, magnetic field and the vertical height, in order of importance. (1) Growth of ω₀, which corresponds to the decrease of the effective transverse size d in InAs QDs, suppresses the increase of the rate Γ. (2) The temperature T affects the rate Γ evidently, which will reduce the inhibition of ω₀ on Γ. With increase of the temperature from 1 K to 7 K, the spin inversion relaxation rate grows explosively from 10³ s^－1 to 10⁸ s^－1. (3) The rate Γ decreases with the growth of the vertical height z₀ and have the order of magnitude 10⁰－10³ s^-1 at T=1 K, whereas the influence of the temperature increase (at T=6 K) on the rate will gradually exceed that of the height growth. (4) At different frequencies ω₀ all curves of the rate Γ versus magnetic field B have a peak that almost appears at the same field, which is attributed to the contribution of the Zeeman term H ^ Z exceeding that of H ^ _SO since there is a considerable g factor in InAs material.