Infrared and optical spectroscopy are prime experimental techniques in determining the physical phenomena of a solid’s response to electromagnetic radiation.
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Infrared and optical spectroscopy are prime experimental techniques in determining the physical phenomena of a solid’s response to electromagnetic radiation. Optical frequencies refer to visible and ultraviolet light pertaining 12500 -50000 cm 1. The interaction of these frequencies with a solid leads to energy excitations of outer shell electrons giving insight on electron inter-band transitions and plasma oscillations. While, the infrared frequencies are lower in frequency compared to optical having 30 – 12500 cm 1. In this region the solid can absorb the energy which can lead to lattice vibrations, electron intra-band transitions and also plasma oscillations. Thus this broad frequency range, 30 – 50000 cm 1, allows for understanding of charge dynamics, low-energy excitations and electronic band structure [1, 2, 3].
Within the past several years a newly discovered ’state of matter’ called topological insulators has emerged with unique physical properties. Although the name is deceiving they behave as an insulator in the bulk, but have edge (2D case) or surface (3D case) states that allows for the motion of free electrons [4, 5]. The actual skin depth of conducting edges/surfaces is unknown. Their band structure follows from the conventional insulator, meaning there is an energy gap between the valance band and the conduction band, but on the boundary there are these gapless edges or
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surface states that are protected by time reversal symmetry. [4, 5, 6, 7, 8].
Since topological insulators are relatively new materials, knowledge and un- derstanding of their physical properties are limited. At the current time there has been no other research published using infrared and optical spectroscopy. Thus being
ideal to gain insight on their optical properties.