Observation of second sound in a rapidly varying temperature field in Ge

Beardo, Albert; López-Suárez, Miquel; Pérez, Luis Alberto; Sendra, Lluc; Alonso, M.; Melis, Claudio; Bafaluy, J.; Camacho, Juan Pedro M.; Colombo, Luciano; Rurali, Riccardo; Alvarez, F. X.; Reparaz, J. S.

doi:10.48550/arxiv.2007.05487

Cited by 1 publication

(6 citation statements)

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“…The results show that the available experimental data is not the best and some conditions indicate possible crucial problems. According to previous studies and disputes [14,32,33,3,2], it is hard to clearly distinguish the (quasi) ballistic or hydrodynamic phonon transport only by the wave like propagation of heat. So can we provide an approach to distinguish them?…”

Section: Introductionmentioning

confidence: 99%

“…In the absence of time-varying heat source or oscillatory boundaries, the temperature always exponentially decays with time due to involvement of first-order time-derivative in the diffusion equation. However, when the characteristic length/time of the thermal system is comparable to the phonon mean free path/relaxation time [1,2,3,4,5], or when the momentum-conserved normal (N) scattering dominates heat conduction [6,7,8,9], the Fourier's law may be broken [10,11,12,13] and the wave like propagation of heat [14,15,16,17,18,19] may appear.…”

Section: Introductionmentioning

confidence: 99%

“…Apart from hydrodynamic phonon transport [9,23,25,14], some studies also predicted the wave like propagation of heat when the characteristic length/time of the thermal system is comparable to or smaller than the phonon mean free path/relaxation time [37,2,3,5]. In this regime, the (quasi) ballistic phonon transport [13,38] (Fig.…”

Section: Introductionmentioning

confidence: 99%

“…In frequency-domain thermoreflectance (FDTR) experiments [3], when the frequency of time varying heat source increases, the experimental phase shifts and the amplitude of the temperature oscillations can also be observed, which can not be explained by the modified Fourier's law with an effective thermal conductivity. Recently, the wave like propagation of heat has also been observed in a rapidly varying temperature field in Germanium between 7 K and room temperature, where the normal scattering is not strong [2].…”

Section: Introductionmentioning

confidence: 99%

“…and (quasi) ballistic regimes [37,2,3]. Recently, the previous NaF experiments [23,40] of second sound and ballistic phonon propagation were quantitatively analyzed [37].…”

Section: Introductionmentioning

confidence: 99%

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A novel transient heat conduction phenomenon to distinguish the hydrodynamic and (quasi) ballistic phonon transport

Zhang,

Guo

2021

Preprint

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Many studies have predicted the failure of Fourier's law of thermal conduction due to the existence of wave like propagation of heat. This non-Fourier thermal transport phenomenon can appear in both the hydrodynamic and (quasi) ballistic regimes. Hence, it is not easy to clearly distinguish these two non-Fourier regimes only by the wave like propagation of heat. In this work, the transient heat propagation in homogeneous thermal system is studied based on the phonon Boltzmann transport equation (BTE) under the Callaway model. Given a quasi-one or quasi-two dimensional thermal system with homogeneous environment temperature, at initial moment, a heat source is added suddenly at the center of the system with high temperature, then the heat propagates from the center to the outer. Numerical results show that in quasitwo dimensional thermal system, the transient temperature will be lower than the lowest value of initial temperature in the hydrodynamic regime within a certain range of time and space. This phenomenon appears only when the normal scattering dominates heat conduction. Besides, it disappears in quasi-one dimensional thermal system. Similar phenomenon is also observed in thermal system with time varying heat source. This peculiar heat propagation phenomenon of hydrodynamic phonon transport distinguishes it well from (quasi) ballistic phonon transport.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…and (quasi) ballistic regimes [37,2,3]. Recently, the previous NaF experiments [23,40] of second sound and ballistic phonon propagation were quantitatively analyzed [37].…”

Section: Introductionmentioning

confidence: 99%

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