Localized Torsional Modes in a Nanowire Superlattice with a Defect Layer

Abstract

We study theoretically the localized vibrational modes in a nanowire superlattice with a defect layer. We focus on azimuthally symmetric torsional modes and calculate the eigenfrequencies of the localized modes. The localized modes are generated within frequency gaps determined by the periodicity of the nanowire superlattice. Furthermore, the radial confinement of vibration generates a critical frequency. When the frequency is lower than this critical frequency, a wave number defined in the defect layer becomes an imaginary number. We show that the localized modes can be generated only above the critical frequency.