期刊
ACS PHOTONICS
卷 5, 期 4, 页码 1241-1249出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsphotonics.7b00945
关键词
titanium dioxide; ultrafast dynamics; electron cooling; two-dimensional spectroscopy; nanoparticles; exciton optical nonlinearities
类别
资金
- Swiss NSF via the NCCR:MUST
- Swiss NSF (PNR 70) [206021-157773, 20020-153660, 407040-154056]
- European Research Council [H2020 ERCEA 695197 DYNAMOX]
- Swiss National Science Foundation (SNF) [206021_157773] Funding Source: Swiss National Science Foundation (SNF)
The recent identification of strongly bound excitons in room temperature anatase TiO2 single crystals and nanoparticles underscores the importance of bulk many-body effects in samples used for applications. Here, for the first time, we unravel the interplay between many-body interactions and correlations in highly excited anatase TiO2 nanoparticles using ultrafast two-dimensional deep-ultraviolet spectroscopy. With this approach, under nonresonant excitation, we disentangle the optical nonlinearities contributing to the bleach of the lowest direct exciton peak. This allows us to clock the ultrafast time scale of the hot electron thermalization in the conduction band with unprecedented temporal resolution, which we determine to be <50 fs, due to the strong electron-phonon coupling in the material. Our findings call for the design of alternative resonant excitation schemes in photonics and nanotechnology.
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