Abstract
Lithium tantalate is technologically one of the most important ferroelectric materials with a low poling field that has several applications in the field of photonics and memory switching devices. In a Hamiltonian system, such as dipolar system, the polarization behavior of such ferroelectrics can be well-modeled by 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 nonlinearity and also impurities (as antisite tantalum defects) in the structure, dissipative effects are observed and hence dissipative breathers are studied here. 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. 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 tantalum defects in the system, i.e., a point of easier switching within the limited amount of data on poling field, which is related to Landau coefficient (read, nonlinearity). Secondly, in a non-periodic boundary condition, 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 applications. Hence, the importance of both the methods for characterizing quantum breathers is shown in these perspectives.
Highlights
IntroductionIn the field of applied physics, one of the most investigated materials is ferroelectric, which has important applications as memory switching (Fu and Cohen 2000; Lines and Glass 1977; Kim et al 2002; Bandyopadhyay and Ray 2004) and in nonlinear optical communications (Gahagan et al 1999), non-volatile memory devices (Dawber et al 2005; Catalan et al 2007), and many others (Kim et al 2001; Bandyopadhyay et al 2010)
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
The paper is organized as follows: in ‘‘Theoretical development’’, we first present some details of spectral collocation method to develop space–time evolution of polarization plots for overall view of classical breathers in ‘‘K-G equation and classical breathers’’, we present the general mathematical model for two-phonon bound states (TPBS) parameters and after second quantization on K-G lattice is done with Bosonic operators along with our method of computation in ‘‘Quantum breathers’’
Summary
In the field of applied physics, one of the most investigated materials is ferroelectric, which has important applications as memory switching (Fu and Cohen 2000; Lines and Glass 1977; Kim et al 2002; Bandyopadhyay and Ray 2004) and in nonlinear optical communications (Gahagan et al 1999), non-volatile memory devices (Dawber et al 2005; Catalan et al 2007), and many others (Kim et al 2001; Bandyopadhyay et al 2010). Lithium tantalate with a low poling field appears to be a promising candidate as a key photonic material for a variety of devices: such as optical parametric oscillators, nonlinear frequency converters, electro-optics and second-order nonlinear optical material, holography, etc Many of such applications include important nanodevices (Bandyopadhyay et al 2010; Waser 2005; Giri et al 2011a). It arises in certain crystal systems that undergo second-order structural changes below the Curie temperature, which results in the development of spontaneous polarization This can be explained by Landau–Ginzburg free energy functional (Kim et al 2002; Bandyopadhyay and Ray 2004; Bandyopadhyay et al 2010). This behavior is nonlinear in terms of hysteresis of polarization (P) and electric field (E) vectors
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