Lithium niobate and lithium tantalate are technologically very important
ferroelectric materials with a low poling field that have several applications
in the field of photonics and memory switching devices. In a Hamiltonian system,
such as dipolar system, the modal dynamics of such ferroelectrics can be
well-modeled by a nonlinear Klein-Gordon (K-G) equation. Due to strong
localization coupled with discreteness in a nonlinear K-G lattice, there is a
formation of breathers and multi-breathers that manifest in the localization
peaks across the domains in polarization-space-time plot. Due to the presence
of impurities in the structure, dissipative effects are observed. To probe the
quantum states related to discrete breathers, the same K-G lattice is quantized
to give rise to quantum breathers (QBs) that are explained by a periodic
boundary condition (Bloch state). The gap between the localized and delocalized
phonon-band is a function of impurity content that is again related to the
effect of pinning of domains due to antisite defects, i.e. a point of easier
switching, which is related to Landau coefficient (read, nonlinearity).
Secondly, in a non-periodic boundary condition approach, the temporal evolution
of quanta shows interesting behavior in terms of ‘critical’ time of
redistribution of quanta that is proportional to QB’s lifetime in femtosecond
having a possibility for THz and other applications in quantum computation. Hence, the importance of both of these methods
for characterizing quantum breathers is shown in these perspectives.
In Book (January, 2014): "Computational and Experimental Chemistry", (Chapter: New
Developments in Computational and Experimental Chemistry), Publisher: Apple
Academic Press, New Jersey
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