耦合锗量子点中空穴态对称特性研究

Asymmetry of hole states in vertically coupled Ge double quantum dot

分别采用单带重空穴近似和六带Kronig-Penney模型,对垂直耦合锗量子点在不同耦合距离下的空穴态特性进行了计算,并探讨了自旋-轨道的相互作用对空穴态对称性的影响.计算结果表明:多带耦合的框架下,随着量子点垂直间距的增大,空穴基态从成键态转变为反键态,而且价带基态能级和第一激发态能级发生反交叉现象,这与单带模型下得到的相应结果存在较大差异.通过分析六带模型计算得到的成、反键态波函数,轻、重空穴态和自旋-轨道分裂态对特征空穴态波函数的贡献比例随着量子点垂直间距的增大发生了转变,并最终导致量子点空穴基态波函数由成键态转变为反键态.

The two lowest single-particle hole states in the vertically coupled Ge/Si double layer quantum dots are investigated numerically by using the single-band heavy hole effective mass approximation and six-band Kronig-Penney model, re-spectively. The calculated results indicate that within the frame of several-band coupled model, the bonding-antibonding ground-state transition and a bonding-antibonding energy anti-crossover phenomenon are observed with interdot dis-tance increasing. These results have not been observed previously in those single-band model calculations. The analysis of the wavefunction component of bonding-antibonding hole state shows that the contribution ratios of light, heavy and spin-orbital-split-off hole states to the characteristic hole wavefunction vary with the increase of the vertical coupled distance, resulting in the ground state wavefunction changing from bonding states to antibonding ones finally.