Isotopic Superlattices for Perfect Phonon Reflection

Many efforts in material science have been made to hinder heat conductivity by phonons while maintaining reasonable electrical conductivity. Herein we present calculations for a completely novel technological approach that can be implemented in a wide range of thermoelectric materials, which leads to almost complete blockade of thermal conductivity due to phonon propagation but leaves the electrical conductivity unaltered. Suitable parameters for the fabrication of such metamaterials are presented, resulting in tremendously increased ZT -values for thermoelectric devices. In addition, feasibility studies for combinations with low-dimensional electronic materials are presented.