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arXiv · 2507.19794

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

Daiki Ootsuki·Akitoshi Nakano·Urara Maruoka·Takumi Hasegawa·Masashi Arita·Miho Kitamura·Koji Horiba·Teppei Yoshida·Ichiro Terasaki
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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.

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Daiki Ootsuki, Akitoshi Nakano, Urara Maruoka, Takumi Hasegawa, Masashi Arita, Miho Kitamura, Koji Horiba, Teppei Yoshida, Ichiro Terasaki. 2025-09-15. Band-selective Plasmonic Polaron in Thermoelectric Semimetal Ta$_2$PdSe$_6$ with ultra-high power factor. https://doi.org/10.1038/s41535-026-00858-8

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