Ultrafast Symmetry Control in Photoexcited Quantum Dots
- Argonne National Laboratory (ANL), Argonne, IL (United States); Middlebury College
- University of Chicago, IL (United States)
- University of Vermont, Burlington, VT (United States)
- Middlebury College, VT (United States)
- Brown University, Providence, RI (United States)
- Stanford University, CA (United States); SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
- Northwestern University, Evanston, IL (United States)
- Argonne National Laboratory (ANL), Argonne, IL (United States)
- SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
- Northwestern University, Evanston, IL (United States); Argonne National Laboratory (ANL), Argonne, IL (United States)
- University of Chicago, IL (United States); Argonne National Laboratory (ANL), Argonne, IL (United States)
Symmetry control is essential for realizing unconventional properties, such as ferroelectricity, nonlinear optical responses, and complex topological order, thus it holds promise for the design of emerging quantum and photonic systems. Nevertheless, fast and reversible control of symmetry in materials remains a challenge, especially for nanoscale systems. Here, reversible symmetry changes are unveiled in colloidal lead chalcogenide quantum dots on picosecond timescales. Using a combination of ultrafast electron diffraction and total X-ray scattering, in conjunction with atomic-scale structural modeling and first-principles calculations, it is revealed that symmetry-broken lead sulfide quantum dots restore to a centrosymmetric phase upon photoexcitation. The symmetry restoration is driven by photoexcited electronic carriers, which suppress lead off-centering for about 100 ps. Furthermore, the change in symmetry is closely correlated with the electronic properties, and the bandgap transiently red-shifts in the symmetry-restored quantum dots. Overall, this study elucidates reversible symmetry changes in colloidal quantum dots, and more broadly defines a new methodology to optically control symmetry in nanoscale systems on ultrafast timescales.
- Research Organization:
- Middlebury College, VT (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF); National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE)
- Grant/Contract Number:
- SC0023425; AC02-06CH11357; AC02-76SF00515
- OSTI ID:
- 2491425
- Journal Information:
- Advanced Materials, Journal Name: Advanced Materials Journal Issue: 4 Vol. 37; ISSN 0935-9648
- Publisher:
- WileyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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