Fluctuation-induced structural forces in nematic films

In a brief review of the theory of pseudo-Casimir interaction in nematic liquid crystals, we describe long- and short-range fluctuation-induced forces in these materials and discuss the role of the anchoring strength in this context. We also analyze the pretransitional behavior of the interaction in the vicinity of the clearing point.

Authorship

P. Ziherl

J. Stefan Institute, Ljubljana, SloveniaJ. Stefan InstituteSloveniaLjubljana, SloveniaJ. Stefan Institute, Ljubljana, Slovenia

University of Ljubljana, Department of Physics, Ljubljana, SloveniaUniversity of LjubljanaSloveniaLjubljana, SloveniaUniversity of Ljubljana, Department of Physics, Ljubljana, Slovenia

S. Zumer

J. Stefan Institute, Ljubljana, SloveniaJ. Stefan InstituteSloveniaLjubljana, SloveniaJ. Stefan Institute, Ljubljana, Slovenia

University of Ljubljana, Department of Physics, Ljubljana, SloveniaUniversity of LjubljanaSloveniaLjubljana, SloveniaUniversity of Ljubljana, Department of Physics, Ljubljana, Slovenia

R. Podgornik

J. Stefan Institute, Ljubljana, SloveniaJ. Stefan InstituteSloveniaLjubljana, SloveniaJ. Stefan Institute, Ljubljana, Slovenia

University of Ljubljana, Department of Physics, Ljubljana, SloveniaUniversity of LjubljanaSloveniaLjubljana, SloveniaUniversity of Ljubljana, Department of Physics, Ljubljana, Slovenia

SCIMAGO INSTITUTIONS RANKINGS

University of Ljubljana, Department of Physics, Ljubljana, SloveniaUniversity of LjubljanaSloveniaLjubljana, SloveniaUniversity of Ljubljana, Department of Physics, Ljubljana, Slovenia

J. Stefan Institute, Ljubljana, SloveniaJ. Stefan InstituteSloveniaLjubljana, SloveniaJ. Stefan Institute, Ljubljana, Slovenia

Figures

Figures (5)

Thumbnail

Figure 1.
The system considered consists of two identical parallel plates immersed in a nematic liquid crystal.

Thumbnail

Figure 2.
The five nematic degrees of freedom can be visualized by a block such that the anisotropy of its sides is proportional to the eigenvalues of the order parameter. Fluctuations of the degree of order are represented by the breathing mode (a), biaxial fluctuations modify the ratio of the short sides and rotate the block about its long axis (b), and director fluctuations correspond to the rotation of the block about the two short axes (c).

Thumbnail

Figure 3.
Pretransitional behavior of the fluctuation-induced force in a nematic liquid crystal is depicted most transparently by plotting the ratio of the temperature-dependent total fluctuation-induced force and the director modes' force. On approaching T_NI from the nematic phase (solid line), the range of the short-range component of the fluctuation-induced force increases and in typical materials it reaches » 10 nm at the clearing point. In the isotropic phase (dashed line), the fluctuation-induced force is entirely short-range and its correlation length decreases on heating.

Thumbnail

Figure 4.
Reduction factor of the interaction induced by the director modes reaches a minimum of 0.077 at d/l = 1.230. The asymptotic expansion of R for large d/l is given by 1-6l/d (dashed line).

Thumbnail

Figure 5.
Reduction factor for fluctuations with finite correlation length for l/x = 0.1,0.5,1,2, and 10: in case of rather strong anchoring, R is a nonmonotonic function of the reduced distance, d/x, and in case of rather weak anchoring R decreases monotonically towards the large d/x limit.

Figure 1. The system considered consists of two identical parallel plates immersed in a nematic liquid crystal.

Figure 2. The five nematic degrees of freedom can be visualized by a block such that the anisotropy of its sides is proportional to the eigenvalues of the order parameter. Fluctuations of the degree of order are represented by the breathing mode (a), biaxial fluctuations modify the ratio of the short sides and rotate the block about its long axis (b), and director fluctuations correspond to the rotation of the block about the two short axes (c).

Figure 3. Pretransitional behavior of the fluctuation-induced force in a nematic liquid crystal is depicted most transparently by plotting the ratio of the temperature-dependent total fluctuation-induced force and the director modes' force. On approaching T_NI from the nematic phase (solid line), the range of the short-range component of the fluctuation-induced force increases and in typical materials it reaches » 10 nm at the clearing point. In the isotropic phase (dashed line), the fluctuation-induced force is entirely short-range and its correlation length decreases on heating.

Figure 4. Reduction factor of the interaction induced by the director modes reaches a minimum of 0.077 at d/l = 1.230. The asymptotic expansion of R for large d/l is given by 1-6l/d (dashed line).

Figure 5. Reduction factor for fluctuations with finite correlation length for l/x = 0.1,0.5,1,2, and 10: in case of rather strong anchoring, R is a nonmonotonic function of the reduced distance, d/x, and in case of rather weak anchoring R decreases monotonically towards the large d/x limit.

How to cite

copy

Sociedade Brasileira de Física Caixa Postal 66328, 05315-970 São Paulo SP - Brazil, Tel.: +55 11 3091-6922, Fax: (55 11) 3816-2063 - São Paulo - SP - Brazil
E-mail: sbfisica@sbfisica.org.br

Acompanhe os números deste periódico no seu leitor de RSS

Versão para download de PDF

PDF

Inglês

Versões e tradução automática

Versão original do texto

English

Tradução automática

Google Translator
Microsoft Translator

Como citar

RIS

BIBTEX

Outros formatos de citação e exportação:

SciELO - Scientific Electronic Library Online
Rua Dr. Diogo de Faria, 1087 – 9º andar – Vila Clementino 04037-003 São Paulo/SP - Brasil
E-mail: scielo@scielo.org

Leia a Declaração de Acesso Aberto

Métricas

Fluctuation-induced structural forces in nematic films

PlumX