Low Temperature Physics: 29, 414 (2003); https://doi.org/10.1063/1.1542505 (8 pages)
Surface and quasi-surface states in strongly anisotropic layered crystal
A.M. Kosevich, P.A. Minaev, E.S. Syrkin
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Science of Ukraine, 47 Lenin Ave., Kharkov, 61103, Ukraine
1153 Baker Ave., Shenectady, NY 12309, USA
Received July 25, 2002
In the first part of the paper different types of the surface waves are considered within a longwave limit for a relatively simple model of a strongly anisotropic layered crystal. Special solutions of the lattice dynamics equations possessing frequencies both out of the continous spectrum band of the ideal lattice (surface states) and inside this band (quasi-surface states) are obtained. In the second part the shear waves localized near a monoatomic layer adsorbed by the surface of strongly anisotropic layered crystal are considered at a microscopic level for a vector lattice model. This model satisfies the conditions of translational and rotational invariance and elastic stability. It is shown that the noncentral interaction between atoms gives rise, in some cases, to surface
shear waves of special type. These waves can exist only in a definite interval of the two-dimensional wave-vectors and have a nonmonotonic behaviour of the decay parameter.