Graded thermal conductivity in 2D and 3D homogeneous hotspot systems

Efficient mechanical modulation of the phonon thermal conductivity of Mo6S6 nanowires

“…† As indicated, the normal process was found to be around 2 orders of magnitude stronger than the Umklapp process in the low-frequency range (<1 THz), thereby explaining that the extremely high κ lf of the Mo 6 S 6 nanowire might partially be caused by the hydrodynamic effects. 66,67 To provide physical insights into the deformation-induced crossover in κ lf , the vibrational density of states (vDOS) of the molecular structures in the wire-axial direction were calculated. Fig.…”

Transient hydrodynamic phonon transport in two-dimensional disk geometry

“…The phonon dispersion and polarization of graphene are calculated by the Vienna Ab initio Simulation Package (VASP) combined with phonopy. Details can be found in our previous paper 40 . The physical nature of the photothermal conversion including photon-electron-phonon coupling is quite complicated 47,50,55 , so that here we assume that all phonons reach thermal equilibrium after absorbing the energy coming from heating laser beam 48 and the spectral weight is After the heat source is removed, the evolution of the probe temperature under different environment temperature are shown in Fig.…”

“…Due to symmetry, the θ ∈ [0, π] is discretized with the N θ -point Gauss-Legendre quadrature. In graphene disk, 300 discretized frequency bands are considered 34,40 and the mid-point rule is used for the numerical integration of the frequency space. For all cases, N θ = 50 and CFL = 0.04 − 0.4.…”

“…For all cases, N θ = 50 and CFL = 0.04 − 0.4. The present discretizations of the phase space are enough for all phonon transport regimes according to our previous experience 22,34,40,41 .…”

Non-monotonic heat dissipation phenomenon in close-packed 2D and 3D hotspot system

“…The first is the ballistic phonon transport [8], which happens when the systems characteristic length/time is comparable to or much smaller/shorter than the phonon mean free path [9,10,11,12]/relaxation time [13,14,15,16]. The second arises from small-scale heat sources [17,18,19,20,21,22,23]. When a hotspot with small size is added in a bulk material, if the phonon mean free path is comparable to or much larger than the size of hotspot, phonons emitted from the hotspot do not suffer sufficient phonon-phonon scattering near the hotspot region so that quasiballistic phonon transport occurs even if there is no boundary or interface scattering inside the systems [19,20,22].…”