Experimental determination of the phase-transition critical exponents and by integrating methods

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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
dc.date.issued 1998
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
dc.publisher College Park, MD : American Physical Society
dc.relation.ispartofseries Physical Review B 57 (1998), Nr. 6
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
dc.type Text
dc.relation.issn 10980121
dc.relation.doi https://doi.org/10.1103/PhysRevB.57.3345
dc.bibliographicCitation.issue 6
dc.bibliographicCitation.volume 57
dc.bibliographicCitation.firstPage 3345
dc.bibliographicCitation.lastPage 3355
dc.description.version publishedVersion
tib.accessRights frei zug�nglich

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