Band-selective Plasmonic Polaron in Thermoelectric Semimetal Ta${}_2$PdSe${}_6$ with ultra-high power factor

Abstract

We report the electronic structure of the thermoelectric semimetal Ta${}_2$PdSe${}_6$ with a large thermoelectric power factor and giant Peltier conductivity by means of angle-resolved photoemission spectroscopy (ARPES). The ARPES spectra reveal the coexistence of a sharp hole band with a light electron mass and a broad electron band with a relatively heavy electron mass, which originate from different quasi-one-dimensional (Q1D) chains in Ta${}_2$PdSe${}_6$. Moreover, the electron band around the Brillouin-zone (BZ) boundary shows a replica structure with respect to the energy originating from plasmonic polarons due to electron-plasmon interactions. The different scattering effects and interactions in each atomic chain lead to asymmetric transport lifetimes of carriers: a large Seebeck coefficient can be realized even in a semimetal. Our findings pave the way for exploring the thermoelectric materials in previously overlooked semimetals and provide a new platform for low-temperature thermoelectric physics, which has been challenging with semiconductors.

7 pages, 4 figures

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Cited by in corpus (1)

• Valley-dependent electron-phonon scattering in thermoelectric semimetal Ta${}_2$PdSe${}_6$