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Giebink NC, Johnson ER, Saucedo SR, et al. Dynamics of laser-induced electroconvection pulses. Phys Rev E Stat Nonlin Soft Matter Phys. 2004;69(6):066303doi: 10.1103/PhysRevE.69.066303.
Giebink, N. C., Johnson, E. R., Saucedo, S. R., Miles, E. W., Vardanyan, K. K., Spiegel, D. R., & Allen, C. C. (2004). Dynamics of laser-induced electroconvection pulses. Physical review. E, Statistical, nonlinear, and soft matter physics, 69(6), 066303. https://doi.org/10.1103/PhysRevE.69.066303
Giebink, N C, et al. "Dynamics of laser-induced electroconvection pulses." Physical review. E, Statistical, nonlinear, and soft matter physics vol. 69,6 (2004): 066303. doi: https://doi.org/10.1103/PhysRevE.69.066303
Giebink NC, Johnson ER, Saucedo SR, Miles EW, Vardanyan KK, Spiegel DR, Allen CC. Dynamics of laser-induced electroconvection pulses. Phys Rev E Stat Nonlin Soft Matter Phys. 2004 Jun;69(6):066303. doi: 10.1103/PhysRevE.69.066303. Epub 2004 Jun 04. PMID: 15244722.
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Phys Rev E Stat Nonlin Soft Matter Phys. 2004 Jun;69(6):066303. doi: 10.1103/PhysRevE.69.066303. Epub 2004 Jun 04.

Dynamics of laser-induced electroconvection pulses.

Physical review. E, Statistical, nonlinear, and soft matter physics

N C Giebink, E R Johnson, S R Saucedo, E W Miles, K K Vardanyan, D R Spiegel, C C Allen

Affiliations

  1. Department of Physics and Astronomy, Trinity University, San Antonio, Texas, USA.

PMID: 15244722 DOI: 10.1103/PhysRevE.69.066303

Abstract

We first report that, for planar nematic 4-methoxy-benzilidene-4-butylaniline (MBBA), the electroconvection threshold voltage has a nonmonotonic temperature dependence, with a well-defined minimum, and a slope of about -0.12 V/degrees C near room temperature at 70 Hz. Motivated by this observation, we have designed an experiment in which a weak continuous-wave absorbed laser beam with a diameter comparable to the pattern wavelength generates a locally supercritical region, or pulse, in dye-doped MBBA. Working 10-20 % below the laser-free threshold voltage, we observe a steady-state pulse shaped as an ellipse with the semimajor axis oriented parallel to the nematic director, with a typical size of several wavelengths. The pulse is robust, persisting even when spatially extended rolls develop in the surrounding region, and displays rolls that counterpropagate along the director at frequencies of tenths of Hz, with the rolls on the left (right) side of the ellipse moving to the right (left). Systematic measurements of the sample-voltage dependence of the pulse amplitude, spatial extent, and frequency show a saturation or decrease when the control parameter (evaluated at the center of the pulse) approaches approximately 0.3. We propose that the model for these pulses should be based on the theory of control-parameter ramps, supplemented with new terms to account for the advection of heat away from the pulse when the surrounding state becomes linearly unstable. The advection creates a negative feedback between the pulse size and the efficiency of heat transport, which we argue is responsible for the attenuation of the pulse at larger control-parameter values.

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