dc.identifier.uri |
http://dx.doi.org/10.15488/2788 |
|
dc.identifier.uri |
http://www.repo.uni-hannover.de/handle/123456789/2814 |
|
dc.contributor.author |
Voges, C.
|
|
dc.contributor.author |
Pfnür, Herbert
|
|
dc.date.accessioned |
2018-02-19T14:57:15Z |
|
dc.date.available |
2018-02-19T14:57:15Z |
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dc.date.issued |
1998 |
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dc.identifier.citation |
Voges, C.; Pfnür, H.: Experimental determination of the phase-transition critical exponents and by integrating methods. In: Physical Review B 57 (1998), Nr. 6, S. 3345-3355. DOI: https://doi.org/10.1103/PhysRevB.57.3345 |
|
dc.description.abstract |
Integrating methods in low-energy electron diffraction—turning the instrument to low resolution in k∥—can reliably be used to study critical properties of continuous two-dimensional phase transitions and to determine critical exponents α and η. We performed systematic tests of the conditions under which an energylike power dependence of the diffracted intensity of superstructure beams can be observed in order-disorder phase transitions of adsorbed atomic layers belonging to three- and four-state Potts universality classes. As experimental examples, we studied the systems p(2×2)- and (√3×√3)R30°-S/Ru(0001) and (2×2)−2H/Ni(111). We show that above Tc the condition for an energylike singularity, KIξ≫1 (KI: radius of integration in k space, ξ: correlation length) is already reached at KIξ>3, whereas below Tc effective exponents α are already obtained for KIξ<1. Therefore, in the temperature range below Tc this method to determine α turns out to be particularly easy to apply, and we concentrate on the determination of α below Tc in this study. Values of α of 0.67±0.04 and 0.40±0.05 were obtained for four-state Potts and three-state Potts systems, respectively. The latter value indicates small crossover effects to the critical behavior of the peak intensity. These studies were then further extended to the order-disorder transition of p(2×2)−O/Ni(111), which is weakly first order, and to the effects of oxygen impurities in the system (2×2)−2H/Ni(111). We further show that in the limit kξ≫1 the exponent η can be determined from the k∥ dependence of integrated ring intensities around positions of superstructure beams. With the systems mentioned, we demonstrate that the limit of a leading term of critical scattering which is independent of temperature can be reached by carrying out measurements going through the order-disorder phase transitions. Values of η of 0.27±0.10 and of 0.30±0.10 were obtained for the four-state and the three-state Potts systems, in close agreement with theoretical expectations. |
eng |
dc.language.iso |
eng |
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dc.publisher |
College Park, MD : American Physical Society |
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dc.relation.ispartofseries |
Physical Review B 57 (1998), Nr. 6 |
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dc.rights |
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. |
|
dc.subject |
phase transition |
eng |
dc.subject |
low-energy electron diffraction |
eng |
dc.subject |
LEED |
eng |
dc.subject.ddc |
530 | Physik
|
ger |
dc.title |
Experimental determination of the phase-transition critical exponents and by integrating methods |
|
dc.type |
Article |
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dc.type |
Text |
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dc.relation.issn |
10980121 |
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dc.relation.doi |
https://doi.org/10.1103/PhysRevB.57.3345 |
|
dc.bibliographicCitation.issue |
6 |
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dc.bibliographicCitation.volume |
57 |
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dc.bibliographicCitation.firstPage |
3345 |
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dc.bibliographicCitation.lastPage |
3355 |
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dc.description.version |
publishedVersion |
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tib.accessRights |
frei zug�nglich |
|