Heat flux induced blueshift of dominant phonon wavelength and its impact on thermal conductivity

Aymeric Ramière Ramière (1, 2) , Sebastian Volz (3) , Jay Amrit (1)

1 LIMSI - Laboratoire d'Informatique pour la Mécanique et les Sciences de l'Ingénieur
2 LIMMS - Laboratory for Integrated Micro Mechatronics Systems
3 EM2C - Laboratoire d'Énergétique Moléculaire et Macroscopique, Combustion

The concept of dominant phonon wavelength is investigated in systems submitted to a heat flux at low temperatures. Using spectral energy distributions, a treatment of two-dimensional and three-dimensional structures is conducted in parallel. We demonstrate a significant reduction of the dominant phonon wavelength, up to 62%, due to a displacement of the phonon spectrum towards higher frequencies in presence of a heat flux. We name this phenomenon blueshift effect. A formula is provided to directly calculate the corrected dominant phonon wavelength. We illustrate the impact of the blueshift effect by showing that a temperature gradient of 10% at 4K yields a 20% reduction in the thermal conductivity. Therefore, ignoring the blueshift effect in a thermal model can notably alter the physical interpretation of measurements. The results suggest that an appropriate heat flux environment can improve thermoelectric device performances.

Domains: Materials Science [cond-mat.mtrl-sci]; Thermics [physics.class-ph]; Micro and nanotechnologies/Microelectronics

Aymeric Ramière Ramière, Sebastian Volz, Jay Amrit. Heat flux induced blueshift of dominant phonon wavelength and its impact on thermal conductivity. AIP Advances, 2017, 7, pp.015017. ⟨10.1063/1.4971275⟩. ⟨hal-01515099⟩