Enlargement of band gaps on thermal wave crystals by using heterostructures

Thermal wave crystals are periodic structures that support temperature wave oscillations. In these lattices, band gaps exist for heat flow due to interference phenomena. In this work, we demonstrate how heterostructures—a stack of two different lattices—can be used to increase band gaps. We investigate two distinct periodic structures. The first is a biological composite made up of stratum-like and dermal-like materials where we have found a band gap enlargement from 1.93 to 10.08 Hz. The second is composed of two semiconductors, silicon (Si) and germanium (Ge), where we have designed a heterostructure with a band gap ranging 0.096 to 0.17 Thz. The design of heterostructures to increase band gaps is especially useful when there is a low contrast of material parameters, as is the case of semiconductors. •Different thermal wave crystal lattices were investigated for their ability to overlap band gaps in order to produce a heterostructure with an enlarged band gap.•Using a band map, investigate the larger band gap of a thermal wave crystal as a function of the filling fraction.•Temperature wave transmission through a finite thermal wave crystal heterostructure is calculated to confirm the presence of band gaps in a heterostructure.•Analysis of two different multilayers, one made of biological components and the other of semiconductors, revealed enlarged band gaps in the Hz and Thz frequency ranges, respectively.