7 research outputs found
Effective index of refraction, optical rotation, and circular dichroism in isotropic chiral liquid crystals
This paper concerns optical properties of the isotropic phase above the
isotropic-cholesteric transition and of the blue phase BP III. We introduce an
effective index, which describes spatial dispersion effects such as optical
rotation, circular dichroism, and the modification of the average index due to
the fluctuations. We derive the wavelength dependance of these spatial
dispersion effects quite generally without relying on an expansion in powers of
the chirality and without assuming that the pitch of the cholesteric is
much shorter than the wavelength of the light , an approximation which
has been made in previous studies of this problem. The theoretical predictions
are supported by comparing them with experimental spectra of the optical
activity in the BP III phase.Comment: 15 pages and 7 figures. Submitted to PR
Nonlinear Switching in Surface Stabilized Ferroelectric Liquid Crystals
Dynamics of director field switching in the vicinity of the SmA-SmC phase transition is
studied by means of light scattering. The resonance dependence of scattered intensity on the
electric field frequency is observed. The resonance scattering disappears at lower temperatures. The
observed anomaly is consistently explained in the framework of the nonlinear kink switching model.
The results of this work demonstrate that in the case of materials with high spontaneous
polarization this mechanism is predominant
Modulated Structures of the Smectic-C Phase in Free-Standing Films withHigh Spontaneous Polarization
PHYS. REV.
The use of a piezoelectric force sensor in the magnetic force microscopy of thin permalloy films
Anomalous multi-order Raman scattering in LaMnO3: a signature of quantum lattice effects in a Jahn-Teller crystal
The multi-order Raman scattering is studied up to a fourth order for
a detwinned LaMnO3 crystal. Based on a comprehensive data analysis of the
polarisation-dependent Raman spectra, we show that the anomalous features in the
multi-order scattering could be the sidebands on the low-energy mode at about 25
cm−1. We suggest that this low-energy mode stems from the tunneling transition
between the potential energy minima arising near the Jahn-Teller Mn3+ ion due to the
lattice anharmonicity, and the multi-order scattering is activated by this low-energy
electronic motion. The sidebands are dominated by the oxygen contribution to the
phonon density-of-states, however, there is an admixture of an additional component,
which may arise from coupling between the low-energy electronic motion and the
vibrational modes. We suggest that superexchange interaction may be crucial in
driving the system to the regime of the dynamic Jahn-Teller effect, with affordable
barriers for the tunneling between the potential energy minima