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Quantum Monte Carlo Study on Excitonic Complexes in Quantum Structures

量子结构中激子配合物的量子蒙特卡罗研究

基本信息

批准号：
10640303
负责人：
TSUCHIYA Takuma
金额：
$ 2.18万
依托单位：
Japan Advanced Institute of Science and Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

In this research project, we have successfully investigated properties of excitonic complexes or excitons, excitonic molecules, and charged excitons in various quantum structures, using the diffusion Monte Carlo method. This method gives us exact binding energies within a small statistical error under the effective mass approximation and is applicable to any complicated confinement potentials. We have obtained the following results :1. GaAs/AlGaAs type-I quantum wellsWe have found that the biexcitonic binding energies are almost twice of those by variational method. The binding energies for positively charged excitons are smaller than those of biexcitons, and those of negatively charged excitons are smaller than negatively charged ones. For quantum wells narrower than 100 A, the roughness of the heterointerfaces causes lateral confinement of excitonic complexes and resulting strong enhancement of binding energies. This enhancement is observed in recent experiments, and our theoretical … More results reproduce the experimental ones quite well.2. Quantum dotsIt has been found that the binding energies can be negative or can increase strongly for relatively small dots. This comes from the electrostatic potential in a quantum dot resulting from the difference of confinement between an electron and a hole of an exciton in the dot.3. GaAs/AlAs type-II superlatticesBecause of the spatial separation between electron and holes, an exciton in type-II superlattices has dipole moment. Because of the dipole-dipole interaction between these excitons they can bind successively along the growth direction and form an excitonic polymer. The binding energy per excitons of 3 meV is expected.4. Quantum wiresThe properties of excitonie complexes in quantum wires are between those in quantum wells and quantum dots. As in quantum dots, the binding energies can be strongly enhanced, but they cannot be negative. This is because the distance between particles with a repulsive Coulomb interaction between them can be infinity. This means that we can prevent a formation of some kind of excitonic complexes by controlling confinement potentials. Less

在本研究项目中，我们成功地研究了激子复合物或激子，激子分子和带电激子在各种量子结构中的性质，使用扩散蒙特卡罗方法。该方法在有效质量近似下给出了精确的结合能，统计误差很小，适用于任何复杂的禁闭势。我们得到了以下结果：1. GaAs/AlGaAs Ⅰ型量子阱的双激子结合能是变分法的两倍。带正电荷的激子的结合能小于双激子的结合能，带负电荷的激子的结合能小于带负电荷的激子的结合能。对于窄于100 A的量子威尔斯，异质界面的粗糙度导致激子复合物的横向限制，从而导致结合能的强烈增强。在最近的实验中观察到这种增强，我们的理论 ...更多信息结果与实验结果吻合较好.量子点已经发现，对于相对较小的点，结合能可以是负的，或者可以强烈地增加。这是由于量子点中激子的电子和空穴之间的约束差异导致量子点中的静电势。GaAs/AlAs Ⅱ型超晶格由于电子和空穴的空间分离，Ⅱ型超晶格中的激子具有偶极矩。由于这些激子之间的偶极-偶极相互作用，它们可以沿着生长方向连续沿着结合并形成激子聚合物。预计每个激子的结合能为3 meV。量子线中激子复合物的性质介于量子威尔斯和量子点中激子复合物的性质之间。在量子点中，结合能可以被强烈地增强，但它们不能是负的。这是因为具有排斥库仑相互作用的粒子之间的距离可以是无穷大。这意味着我们可以通过控制限制势来防止某种激子复合物的形成。少