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- Csore, A., et al.
(author)
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Towards identification of silicon vacancy-related electron paramagnetic resonance centers in 4H-SiC
- 2021
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In: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 104:3
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Journal article (peer-reviewed)abstract
- The negatively charged silicon vacancy (V-Si(-)) in silicon carbide (SiC) is a paramagnetic and optically active defect in hexagonal SiC. The V(Si)(- )defect possesses S = 3/2 spin with long spin coherence time, and it can be optically manipulated even at room temperature. Recently, electron spin resonance signals have been observed besides those associated with the V-Si(- ) defects in the 4H polytype of SiC. The corresponding centers share properties akin to those of the V-Si(- ) defects and thus they may be promising candidates for quantum technology applications. However, the exact origin of the new signals is unknown. In this paper, we report V-1-related pair defect models as possible candidates for the unknown centers. We determine the corresponding electronic structures and magneto-optical properties as obtained by density functional theory calculations. We propose models for the recently observed electron paramagnetic resonance centers, and we predict their optical signals for identification in future experiments.
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| 2. |
- Muschitiello, Francesco, et al.
(author)
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New evidence of Holocene atmospheric circulation dynamics based on lake sediments from southern Sweden : a link to the Siberian High
- 2013
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In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 77, s. 113-124
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Journal article (peer-reviewed)abstract
- Oxygen (delta O-18) and carbon (delta C-13) isotope records of calcitic carbonate components (Chara sp. algal encrustations and Bithynia tentaculata gastropod opercula) from a lake-sediment succession on the Baltic Sea island of Gotland, south-eastern Sweden, have been obtained to investigate regional climate dynamics during the Holocene. The hydrological sensitivity of the small lake, particularly in terms of spring snowmelt contribution to the local water budget, provides a means of tracing past changes in the influence of snow-bearing easterly winds across the Baltic Sea Proper, which signifies the wintertime strength of the Siberian High. Repeated episodic depletions in O-18 at the centennial scale correlate with events of increased potassium concentration in the GISP2 ice-core record from Greenland, which indicates a coupling to large-scale fluctuations in atmospheric circulation patterns. A corresponding correlation with simultaneous depletions in C-13 suggests repeated responses of the local lake hydrology to snow-rich winters through decreasing water residence time, perhaps augmented by methanogenesis due to prolonged ice-cover seasons under the influence of an expanding Siberian High. Frequency analysis of the isotopic records reveals well-defined fluctuations at quasi-500-520-, 670-, 830- and 1430-yr periodicities, and a gradually stronger impact of Polar air outbreaks across the southern Baltic Sea region with time after ca 6000 cal. BP.
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| 3. |
- Muschitiello, Francesco
(author)
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New insights into past atmospheric circulation dynamics
- 2014
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Licentiate thesis (other academic/artistic)abstract
- Climate change associated with shifts in atmospheric circulation patterns has a great influence on ecosystems and societies. To predict future climate change it is important to obtain a detailed understanding of how climate behaved in the past, with special focus on the regional-scale and short-term expressions of changes in atmospheric circulation dynamics. This scientific goal can be pursued by using stable isotope records from terrestrial sequences and/or by comparing several proxy reconstructions that cover broad geographical regions. As such, isotope records have the ability to provide useful information on past changes in precipitation patterns and atmospheric physical characteristics, whereas the examination of multiple reconstructions distributed over a large area give information on the spatio-temporal variability and the direction of physical changes associated with climatic changes.The results presented in this thesis comprise i) the first Holocene stable isotope record from Gotland, which sheds light on past climate variability associated with the Siberian High over the Baltic Sea region, and ii) a comparison of pollenstratigraphic records from densely 14C dated terrestrial sequences, which provides insight into the spatial and temporal succession of vegetation shifts at the onset of the Younger Dryas cold event over northern Europe.The findings shown in these studies stress the value of using isotope records to assess past regional atmospheric circulation patterns and show the efficacy of examining well-dated networks of climate reconstructions to better understand spatio-temporal propagations of past atmospheric perturbations.
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