Direct measurement of coherent thermal phonons in Bi2Te3/Sb2Te3 superlattice


F. He, Wu, W., and Wang, Y., “Direct measurement of coherent thermal phonons in Bi2Te3/Sb2Te3 superlattice,” Applied Physics A, vol. 122, pp. 777, 2016.
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Coherent thermal phonons (CTPs) play an important role in thermal transport in superlattice (SL) structures. To have a profound understanding of CTP transport in SL, direct measurement of CTP properties is necessary. In this study, coherent phonon spectroscopy has been utilized to generate and detect CTP in Bi2Te3/Sb2Te3 SL. Phonon lifetimes have been extracted from experimental data, with which mode-wise thermal conductivities have been calculated. Comparing with bulk Bi2Te3, the estimated mode-wise thermal conductivity of longitudinal acoustic phonons shifts to higher frequencies, due to constructive coherent phonon interference. Our results suggest that it is possible to use SL structure to manipulate coherent phonon propagation and to tailor thermal conductivity.


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