Srivastava Ajit, Imamoğlu Ataç
Institute of Quantum Electronics, ETH Zürich, CH-8093 Zürich, Switzerland.
Phys Rev Lett. 2015 Oct 16;115(16):166802. doi: 10.1103/PhysRevLett.115.166802.
The geometry of electronic bands in a solid can drastically alter single-particle charge and spin transport. We show here that collective optical excitations arising from Coulomb interactions also exhibit unique signatures of Berry curvature and quantum geometric tensor. A nonzero Berry curvature mixes and lifts the degeneracy of l≠0 states, leading to a time-reversal-symmetric analog of the orbital Zeeman effect. The quantum geometric tensor, on the other hand, leads to l-dependent shifts of exciton states that is analogous to the Lamb shift. Our results provide an explanation for the nonhydrogenic exciton spectrum recently calculated for transition-metal dichalcogenides. Numerically, we find a Berry curvature induced splitting of ∼10 meV between the 2px±i2py states of WSe2.
固体中电子能带的几何结构可极大地改变单粒子电荷和自旋输运。我们在此表明，由库仑相互作用产生的集体光学激发也展现出贝里曲率和量子几何张量的独特特征。非零的贝里曲率混合并解除了(l≠0)态的简并，导致了轨道塞曼效应的时间反演对称类似物。另一方面，量子几何张量导致激子态的(l)依赖位移，这类似于兰姆位移。我们的结果为最近计算的过渡金属二硫属化物的非氢激子光谱提供了解释。在数值上，我们发现(WSe₂)的(2px±i2py)态之间由贝里曲率引起的分裂约为(10)毫电子伏特。
