A computational study of the thermoelectric performance of ultrathin Bi_2Te_3 films

摘要

The ballistic thermoelectric performance of ultrathin films of Bi_2Te_3, ranging in thickness from 1 to 6 quintuple layers, is analyzed using density functional theory combined with the Landauer approach. Our results show that the thinnest film, corresponding to a single quintuple layer, has an intrinsic advantage originating from the particular shape of its valence band, leading to a large power factor and figure-of-merit exceeding bulk Bi_2Te_3. The interaction between the top and bottom topological surface states is key. The thinnest film yields a six-fold increase in power factor compared to bulk.