Dr. Stefan Ochsenbein, a postdoc working with Prof. Daniel Gamelin, Harry and Catherine Jaynne Boand Endowed Professor of Chemistry, is lead author on a new paper published in Nature Nanotechnology reporting the first successful coherent impurity spin manipulation within colloidal semiconductor nanocrystals (also known as quantum dots). Spin effects in semiconductor nanostructures have attracted broad interest for potential spin-based information processing technologies, whether in spin-electronics (“spintronics”) or spin-photonics. Colloidal doped semiconductor nanocrystals present interesting possibilities for constructing devices by solution processing or that involve integration with soft materials (e.g., organics), but their spin properties remain relatively untested. For example, the possibility to manipulate spins within colloidal semiconductor nanocrystals coherently, as would be necessary for many proposed applications, had not been demonstrated until these latest experiments.
In this paper, Ochsenbein and Gamelin describe the first observation of coherent spin manipulation in colloidal doped quantum dots. The observation was made by demonstrating microwave-driven Rabi oscillations within the high-spin ground states of Mn2+ impurity ions doped into colloidal ZnO semiconductor nanocrystals. Their electron spin-echo measurements revealed long spin coherence times approaching 1 µs, sufficient for potential qubit applications with optical excitation. The authors also identified previously unobserved hyperfine interactions between Mn2+ electron spins within the quantum dots and proton nuclear spins outside the quantum dots, revealing an important but previously unrecognized contribution to spin decoherence in such quantum dots.
Read the article: “Quantum oscillations in magnetically doped colloidal nanocrystals.” Ochsenbein, S. T.; Gamelin, D. R., Nature Nanotechnology, 2011, 6, 112–115.