3.2 Linear Deformation-Potential Theory

Linear deformation potential theory has been first justified within the effective mass approximation by Bardeen and Shockley [58] and thus is usually referred to as the Bardeen-Shockley theory. Originally this method has been applied to study the interaction of electrons and acoustic phonons, and later in the theory of strained materials, in particular for thin strained SiGe layers. Within this theory the energy is expanded into a Taylor series in powers of a quantity characterizing the strength of the lattice strain. The expansion is truncated after the first power of this parameter, which renders the theory linear. Neglecting terms of the second order is equivalent to the effective masses being unchanged by the induced strain.
Subsections S. Smirnov: