Electron-phonon coupled hydrodynamics in semimetal TaAs_2
Abstract
Hydrodynamic corrections to diffusive transport can arise when momentum-conserving collisions between quasiparticles become prominent, and they have been documented for both electrons and phonons. An emerging frontier topic is coupled electron-phonon (e-ph) hydrodynamics. Here, through electrical and thermal transport measurements on TaAs2 crystals with different impurity levels, we document the emergence of an e-ph bifluid in the temperature window of 5 to 15 K. Within this range, the lattice thermal conductivity exhibits a faster-than-T^3 temperature dependence, as a consequence of non-monotonic and purity-dependent phonon mean free paths, a signature of phonon Poiseuille flow. However, strong e-ph coupling impedes the emergence of a ballistic regime. This is corroborated by the observation of quantum oscillations in the lattice thermal conductivity. Prominent phonon-mediated momentum exchange between electrons amplifies the violation of the Wiedemann-Franz law and yields a two-order-of-magnitude discrepancy between quantum and transport lifetimes, a signature of electron hydrodynamics in semimetals. Our results imply that in semimetals with optimized e-ph coupling, thanks to matching between the cryogenic phonon wave?length and the Fermi wavelength, momentum and energy flow between the electron and phonon reservoirs as frequently as within each reservoir.
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BibTeX
@misc{jiang2026electronphonon,
title = {{Electron-phonon coupled hydrodynamics in semimetal TaAs_2}},
author = {Shan Jiang and Wei Xie and Xiaokang Li and Kamran Behnia and Zengwei Zhu},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.03517},
eprint = {2609.03517},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.03517},
}
RIS
TY - UNPB
TI - Electron-phonon coupled hydrodynamics in semimetal TaAs_2
AU - Shan Jiang
AU - Wei Xie
AU - Xiaokang Li
AU - Kamran Behnia
AU - Zengwei Zhu
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2609.03517
UR - https://arxiv.org/abs/2609.03517
AB - Hydrodynamic corrections to diffusive transport can arise when momentum-conserving collisions between quasiparticles become prominent, and they have been documented for both electrons and phonons. An emerging frontier topic is coupled electron-phonon (e-ph) hydrodynamics. Here, through electrical and thermal transport measurements on TaAs2 crystals with different impurity levels, we document the emergence of an e-ph bifluid in the temperature window of 5 to 15 K. Within this range, the lattice thermal conductivity exhibits a faster-than-T^3 temperature dependence, as a consequence of non-monotonic and purity-dependent phonon mean free paths, a signature of phonon Poiseuille flow. However, strong e-ph coupling impedes the emergence of a ballistic regime. This is corroborated by the observation of quantum oscillations in the lattice thermal conductivity. Prominent phonon-mediated momentum exchange between electrons amplifies the violation of the Wiedemann-Franz law and yields a two-order-of-magnitude discrepancy between quantum and transport lifetimes, a signature of electron hydrodynamics in semimetals. Our results imply that in semimetals with optimized e-ph coupling, thanks to matching between the cryogenic phonon wave?length and the Fermi wavelength, momentum and energy flow between the electron and phonon reservoirs as frequently as within each reservoir.
ER -