Physics Department, University of Michigan, Ann Arbor, Michigan 48109, USA.
SKKU Advanced Institute of Nano Technology, Sungkyunkwan University, Gyeonggi 16419, Republic of Korea.
Phys Rev Lett. 2019 Aug 2;123(5):057403. doi: 10.1103/PhysRevLett.123.057403.
We perform two-dimensional coherent spectroscopy on CdSe/CdZnS core-shell colloidal quantum dots at cryogenic temperatures. In the two-dimensional spectra, sidebands due to electronic coupling with CdSe lattice LO-phonon modes are observed to have evolutions deviating from the exponential dephasing expected from Markovian spectral diffusion, which is instantaneous and memoryless. Comparison to simulations provides evidence that LO-phonon coupling induces energy-gap fluctuations on the finite timescales of nuclear motion. The femtosecond resolution of our technique probes exciton dynamics directly on the timescales of phonon coupling in nanocrystals.
我们在低温下对 CdSe/CdZnS 核壳胶体量子点进行二维相干光谱学研究。在二维光谱中，观察到与 CdSe 晶格 LO-声子模式的电子耦合引起的边带的演化偏离了马尔可夫谱扩散所预期的指数退相，谱扩散是瞬时且无记忆的。与模拟的比较为 LO-声子耦合在核运动的有限时间尺度上诱导能隙涨落提供了证据。我们的技术具有飞秒分辨率，可以直接在纳米晶体中声子耦合的时间尺度上探测激子动力学。
