Dimensional crossover of polaron dynamics in Nb: SrTiO3/ SrTiO3 superlattices: Possible mechanism of thermopower enhancement


Using optical spectroscopy, we investigated the electrodynamic properties of Nb: SrTiO3/SrTiO3 superlattices. In these superlattices, a large enhancement of the Seebeck coefficient (S) has been reported with decreasing Nb: SrTiO3 layer thickness. By analyzing the optical spectra, we found that the polaron plays an important role in determining the electrodynamic properties of the superlattices. With decreasing Nb: SrTiO3 layer thickness from 11 to 1 unit cell, we observed a threefold enhancement of the polaron effective mass and relaxation time. Such increases were attributed to a dimensional crossover of the polaron from three-dimensional to quasi-two-dimensional. Moreover, the modified nature of the polaron at low dimensions enhanced the thermoelectric properties of the oxide superlattice, by simultaneously increasing S and preventing the decrease in carrier mobility. Our results indicate that strong electron-phonon coupling can provide an alternative pathway in searching for efficient thermoelectric materials. �� 2010 The American Physical Society

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oaioai:repository.hanyang.ac.kr:20.500.11754/85959Last time updated on 2/3/2019

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