On asymmetric propagation on transverse acoustic waves near the structural phase transition in RbH3(SeO3)2

Crystal optical properties of anisotropic optical materials of which the dielectric tensor is spatially modulated with a sinusoidal wave form are studied in the framework of the Jones calculus. Propagation of polarized light along the directions parallel to and far from the optical axes is considered. Polarization of the normal waves of the medium and the Jones matrix of a finite modulated crystal are derived, enabling us to ascertain the parameters of the apparent macroscopic optical activity. The developed model should describe the optical effects in a planewave region of incommensurate phases with the average inversion symmetry, occurring in the A 2 BX 4 family crystals. The boundary conditions for the phase of the modulation wave, which play a key role in crystal optics of incommensurate phases, are discussed. The model predicts a relatively small optical activity in the birefringent crystal sections and negligible or zero effect in the optical axis directions. The conclusions agree well, at least, with the non-contradictory experimental results on optical rotatory power of the A 2 BX 4 crystals. A comparison with the results derived earlier for the square modulation wave proves that the main conclusions of the model do not depend on the exact modulation shape.

Section: Basic Assumptionsmentioning

confidence: 99%

Crystal optical properties of incommensurate phases in the plane-wave modulation region

Kushnir¹

1997

“…As far as the author knows, the failure of C ij to equal C ji has not been observed in incommensurate crystals lacking a screw axis (such as NaNO 2 ). This inequality cannot be due to dispersion (frequency dependence of C ij ), as initially suggested by Dvorak and Esayan [22] and by Scott [23], because later data show that it is true from kHz ultrasonic measurements to GHz Brillouin data. I believe that it arises from lack of mechanical and thermal equilibrium.…”

Section: Mechanical Dis-equilibrium: C Ij = C Jimentioning

confidence: 80%

Flexoelectric spectroscopy

Scott

2013

Flexoelectricity is an increasingly popular subject because it can be extremely large in thin films and permits switching of devices in nonpolar (non-piezoelectric) crystals via application of inhomogeneous stresses. However, recent work has been limited to macroscopic measurement of voltage or strain. Here, we discuss the vibrational spectroscopy of flexoelectricity as a recommended new tool for thin-film characterization, with special emphasis upon incommensurate crystals.

“…That is why it is necessary to take into account the Fourier components ε n i ,m ij (ω, k, ϕ) associated with relatively long-wavelength reciprocal lattice vectors h = 0 [3,12,18]. In the plane-wave modulation region, the most important of these vectors is that determined by the small deviation of the soft-mode wave vector q I C from the corresponding vector q C of the lock-in phase, for it affects notably different physical properties of the IC phases (see [18][19][20]). It is introduced through the relations…”

Section: Introduction Of Macroscopic Dielectric Tensormentioning

confidence: 99%

“…A comparison of ( 8) with (20) enables us to identify q with the reciprocal lattice vectors ±h, of which the indices are equal to n 1 , n 2 = 0, n 3 = ∓r and m = ±s. The modulation wavelength λ q related to q (λ q = a 3 /(sδ)) exceeds by far the lattice parameters a i though is still smaller than the light wavelength λ(λ q /λ ≈ 10 −2 to 10 −1 -see e.g.…”

Section: Introduction Of Macroscopic Dielectric Tensormentioning

confidence: 99%

See 1 more Smart Citation

Symmetry peculiarities of dielectric tensor in incommensurately modulated crystal phases

Kushnir

Lokot

Polovinko

2000

The dielectric permittivity tensor for incommensurately modulated phases in insulating crystals is considered. The main attention is paid to the spatial dispersion giving rise to optical gyration effects and the influence of the modulation phase on those effects. General properties of the dielectric tensor are analysed in relation to the lattice and incommensurate superlattice periodicity requirements, the Onsager principle and the condition of absence of the radiation losses in the optical medium. The structure of the microscopic components of the tensor and a macroscopic averaging procedure for the plane-wave modulation region are discussed. The possibility of existence of an anti-Hermitian part in the dielectric tensor of lossless incommensurate crystals originating from the modulation-induced spatial dispersion is revealed. The performed analysis shows a necessity for introduction into the constitutive equation of the term including spatial derivatives of the optical activity tensor.