Role of ballistic electron transport effects on thermoelectric performance
Phys. Rev. B 113, 035431 – Published 21 January, 2026
DOI: https://doi.org/10.1103/gpc6-1zhn
Abstract
Traditional thermoelectric theory applies to bulk materials and neglects ballistic effects that emerge when the device length approaches the carrier mean free path. This work explores how thermoelectric performance evolves as material length is scaled down, transitioning through diffusive, quasiballistic, and ballistic electron transport regimes. To study this, we develop a coupled electrothermal simulation framework based on the McKelvey-Shockley flux method for modeling ballistic and out-of-equilibrium electron transport, combined with the heat equation and Fourier's law for treating diffusive phonon transport. Using this approach, we simulate thermoelectric generators and coolers with lengths ranging from 1000 nm down to 10 nm. Our results show that ballistic electron transport generally degrades thermoelectric performance relative to bulk materials. However, with the coolers, nonuniform and reduced heat generation associated with nanoscale electron scattering suppresses heat backflow to the cold side, partially offsetting the performance losses. These findings highlight the complex interplay between transport regimes and thermoelectic behavior at the nanoscale.
