Search results for "Spontaneous polarization"
showing 8 items of 8 documents
Influence of strain in the reduction of the internal electric field in GaN/AlN quantum dots grown ona-plane 6H-SiC
2006
The strain state of stacks of GaN/AIN quantum dots (QDs) grown on (0001) and (1120) 6H-SiC has been investigated by means of Raman spectroscopy. Depending on the orientation of the wurtzite axis with respect to the growth direction it is found that the piezoelectric contribution to the electrostatic potential may either reinforce that arising from the spontaneous polarization or oppose it. The experimental results are compared with a theoretical model for the strain and polarization field in QDs of both orientations that allows the calculation of the electrostatic potential in the QDs. Both the experimental results and the theoretical model indicate that the internal electric field and elec…
On the Theory of Domain Structure of Disordered Ferroelectrics
2009
We present a comprehensive analysis of domain structure formation in ferroelectric phase of incipient ferroelectrics with off-center dipole impurities like KTaO 3 :Li, Nb,Na. Our analysis is carried out on the base of effective free energy of disordered ferroelectrics, derived by us earlier. This free energy permits to apply the standard approach to domain structure calculation. Using coupled system of Maxwell equations with those obtained by minimization of above free energy, we calculate the physical characteristics of domain structure as functions of impurity dipoles concentration n. Our theory can be easily generalized for arbitrary temperature and crystal shape including thin films.
An all-organic steroid–D–π-A modular design drives ferroelectricity in supramolecular solids and nano-architectures at RT
2011
Confluence of a modular design approach and self-assembly with a 'steroid-D-π-A' module generates spontaneous polarization in solids and for the first time in nano-architectures constituted from organogels, at room temperature (RT).
Spontaneous symmetry breaking as a resource for noncritically squeezed light
2010
[EN] In the last years we have proposed the use of the mechanism of spontaneous symmetry breaking with the purpose of generating perfect quadrature squeezing. Here we review previous work dealing with spatial (translational and rotational) symmetries, both on optical parametric oscillators and four-wave mixing cavities, as well as present new results. We then extend the phenomenon to the polarization state of the signal field, hence introducing spontaneous polarization symmetry breaking. Finally we propose a Jaynes-Cummings model in which the phenomenon can be investigated at the singlephoton-pair level in a non-dissipative case, with the purpose of understanding it from a most fundamental …
Gelling and the collective dynamics in ferroelectric liquid crystals
2020
Dielectric spectroscopy has been applied to investigate the dynamic behaviour of a ferroelectric liquid crystal in the smectic C* and smectic A phases confined in gel matrices of a fibre like (1D) or platelet like (2D) structure. These gel matrices were obtained from semicarbazide or bis-acylurea derivatives, which self assemble because of their H-bonding motif. The confinement strongly influences the magnitude of the spontaneous polarization and the collective fluctuations of the director detected as the Goldstone-mode. It is thus possible to detect gelation by dielectric spectroscopy. By this method it was possible to follow the destruction and restoration of the gel structure induced by …
Ferroelectric liquid-crystalline elastomers
1994
Ferroelectric liquid crystalline polysiloxanes with high spontaneous polarization and possible applications in nonlinear optics
1990
Noncritical quadrature squeezing through spontaneous polarization symmetry breaking
2010
We discuss the possibility of generating noncritical quadrature squeezing by spontaneous polarization symmetry breaking. We first consider Type II frequency-degenerate optical parametric oscillators but discard them for a number of reasons. Then we propose a four-wave-mixing cavity, in which the polarization of the output mode is always linear but has an arbitrary orientation. We show that in such a cavity, complete noise suppression in a quadrature of the output field occurs, irrespective of the parameter values.