Untersuchung des Einflusses konischer Kreuzungen auf die optoelektronischen Eigenschaften von Festkörperdefekten für neuartige Quantentechnologien.
Physikalische Chemie von Molekülen, Flüssigkeiten und Grenzflächen, Biophysikalische Chemie
Zusammenfassung der Projektergebnisse
A particular class of solid-state defects in materials such as diamond and silicon carbide (SiC), their most famous example being the nitrogen-vacancy centre in diamond, have become a popular playground to harness quantum effects for a variety of potential applications in quantum information and computing, as well as nanoscale magnetic field and temperature sensors, biological markers and single-photon emitters. The utility and functionality of these defects relies on certain key phenomena, such as the establishing of electron spin polarization and the possibility of optical spin read-out, which in turn are a result of a complex interplay of electronic transitions. This project at NTU Singapore was about the application of ultrafast spectroscopy and how it can give valuable insight into the fundamental electronic and vibrational properties and dynamics of these color centers, namely the negatively-charged nitrogen vacancy (NV) and negatively-charged siliconvacancy (SiV) centers in diamond. To this end, transient absorption spectroscopy (TAS) and multidimensional coherent spectroscopy (MDCS) techniques were employed, the latter one jointly with external collaborators. In the course of the project, two of the last remaining timescales of the electronic transitions involved in the spin polarization cycle of the NV center were determined using TAS: the vibrational relaxation in the electronic excited spin triplet state was measured to be 40 fs, an unusually fast and unprecedented value. Additional measurements using MCDS with the group of Daniel Turner confirmed this result and reconciled it with previous conflicting reports. The excited state lifetime of the spin singlet transition was measured to be 100 ps, ten times lower than the previous reported value, which is indicative of the predominantly non-radiative nature of the relaxation process. In collaboration with the group of Steve Cundiff, MCDS measurements at cryogenic temperatures were conducted on NV and SiV centers. For the former, the extracted inhomogeneous broadening showed two distinct Gaussian distributions with center frequencies showing the temperaturedependent shifts in opposite directions. Previous linear absorption measurements had only been sensitive to one of these components, thus missing the second one. Experiments on the SiV centers revealed the existence of radiative and non-radiative emitters showing distinctly different coherence properties and inhomogeneous broadening. Furthermore, preliminary results related to the influence of strain on the fine structure, as well as coherent coupling between SiV centers are promising. Further projects at NTU on the photoionization dynamics of the NV center and excitation-induced heating dynamics of the SiV center are still ongoing and will be concluded at a later stage.
Projektbezogene Publikationen (Auswahl)
- (2018). "Excited-state lifetime of the NV- infrared transition in diamond." Physical Review B 98(9): 094309
R. Ulbricht and Z.-H. Loh
(Siehe online unter https://doi.org/10.1103/PhysRevB.98.094309) - (2018). "Vibrational relaxation dynamics of the nitrogen-vacancy center in diamond." Physical Review B 97(22): 220302(R)
R. Ulbricht, S. Dong, A. Gali, S. Meng and Z.-H. Loh
(Siehe online unter https://doi.org/10.1103/PhysRevB.97.220302) - “Observing long-lived nonradiative electronic states in silicon-vacancy centers in diamond using optical multidimensional coherent spectroscopy”, Proceedings Volume 10916, Ultrafast Phenomena and Nanophotonics XXIII
C. Smallwood; R. Ulbricht; M. W. Day; T. Schröder; K. M. Bates; T. M. Autry; G. Diederich; E. Bielejec; M. E. Siemens; S. T. Cundiff
(Siehe online unter https://doi.org/10.1117/12.2510837) - “Revealing the Orientation Dependence of Coherent Coupling in Silicon-Vacancy Centers in Diamond”, Conference on Lasers and Electro-Optics, 2019
M. W. Day, K. M. Bates, C. L. Smallwood, R. Ulbricht, Travis M. Autry, Rachel C. Owen, Geoffrey Diederich, Tim Schroeder, Edward Bielejec, Mark E. Siemens and Steven T. Cundiff
(Siehe online unter https://doi.org/10.1364/CLEO_QELS.2019.FM3D.1)
