磁振子诱导的杂化使铁磁半导体中的激子变亮
Magnon-induced hybridization brightens excitons in ferromagnetic semiconductors
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中文总结 AI 辅助
本研究通过一维晶格模型精确求解，发现量子磁振子发射吸收可杂化单重态与三重态激子、使暗态变亮并增大激子半径，且对扩展激子效应最强。
中文摘要 AI 辅助
磁性半导体中的激子具有对底层磁序敏感的能量和自旋结构。我们在一个最小的一维晶格模型中研究这种耦合，该模型包含一个传导电子和一个价带空穴，它们在局域量子自旋的铁磁背景中运动，并将电子、空穴和磁振子视为显式分辨的自由度。在零温度下，自旋守恒将相关希尔伯特子空间限制在单磁振子或双磁振子水平，因此该模型可以通过实空间格林函数方法基本精确求解。与冻结自旋近似（其中局域矩被其有序值替代）进行比较，可以识别哪些效应源于量子磁振子的发射和吸收。冻结背景已经消除了激子的自旋简并，并且如果两个载流子与局域矩的耦合强度不同，它还会将单重态与自旋为零的三重态激子混合。量子磁振子的发射和吸收在性质上更进一步：即使在所有冻结自旋效应消失的情况下，它也会使激子能量随交换耦合非线性地分裂和移动；对于具有不等跳跃积分的载流子，它使单重态和自旋为零的三重态激子杂化，从而使暗三重态变亮；并且它增大了激子半径，这反过来通过消除格点上的抵消来增强磁振子 dressing。因此，这些量子效应对扩展的、类万尼尔的激子最强，而这正是通常假设静态（冻结自旋）磁序进行建模的领域。
英文摘要
Excitons in magnetic semiconductors have energies and spin structures that are sensitive to the underlying magnetic order. We study this coupling in a minimal one-dimensional lattice model of a conduction electron and a valence hole moving in a ferromagnetic background of localized quantum spins, treating the electron, the hole, and the magnon(s) as explicitly resolved degrees of freedom. At zero temperature, spin conservation closes the relevant Hilbert subspaces at the one- or two-magnon level, so the model can be solved essentially exactly with a real-space Green's function method. Comparison against a frozen-spin approximation in which the local moments are replaced by their ordered values identifies which effects are due to emission and absorption of quantum magnons. A frozen background already lifts the spin degeneracy of the exciton and, if the two carriers couple with different strengths to the local moments, it mixes the singlet with the spin-zero triplet exciton. The emission and absorption of quantum magnons goes qualitatively further: it splits and shifts the exciton energies nonlinearly in the exchange coupling even when all frozen-spin effects vanish; for carriers with unequal hopping integrals, it hybridizes the singlet and spin-zero triplet excitons, thereby brightening the dark triplet; and it increases the exciton radius, which in turn enhances the magnon dressing by removing an on-site cancellation. These quantum effects are therefore strongest for extended, Wannier-like excitons, which is precisely the regime that is commonly modeled assuming a static (frozen-spin) magnetic order.
发表机构
- University of British Columbia（不列颠哥伦比亚大学）
机构由 AI 辅助整理，请以论文原文为准。
