Abstract
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.
Highlights
The necessity to control heat propagation in ceaselessly smaller devices has been sustaining the growing interest in nanoscale thermal transport for the past two decades.[1,2,3] Today, the electronic technologies are based on the Silicon in the frame of three-dimensional (3D) thermal physics
Having established and consolidated the definitions of dominant phonon wavelength (DPW), we studied its evolution induced by a heat flux imposed by two thermal reservoirs
We show that the effective energy and specific heat density distributions describing the system undergo a shift to higher frequencies that is controlled by the temperatures of the two thermal reservoirs
Summary
The necessity to control heat propagation in ceaselessly smaller devices has been sustaining the growing interest in nanoscale thermal transport for the past two decades.[1,2,3] Today, the electronic technologies are based on the Silicon in the frame of three-dimensional (3D) thermal physics. Thermal conduction properties depend on temperature and phonons frequencies. The effective heat flux flowing from the hot reservoir to the cold reservoir depends on the temperatures of both reservoirs. The DPW becomes significantly smaller as the temperature difference between the thermal reservoirs is decreased, a phenomenon we refer to as blueshift effect. In the limit of small temperature gradient, we show that not considering the heat flux leads to 62% error in the DPW of 2D materials. We detail the calculations describing the behavior of the DPW in 2D and 3D systems between two thermal reservoirs and provide the corrected dominant coefficient as function of the temperature difference. The dependence of the DPW on temperature differences is shown to notably reduce the thermal conductivity. The blueshift effect alters the physical interpretation of experimental results and can be applied to improve the performances of thermoelectric devices
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
