“…5 , 6 . By and large, our spectra are in good agreement with previous theoretical reports 12 – 14 . Figure 1 Cooper Pairs Distribution function and Eliashberg function for Niobium under pressure.…”
In this paper, we report Cooper Pairs Distribution function $${D}_{cp}(\omega ,{T}_{c})$$
D
cp
(
ω
,
T
c
)
for bcc Niobium under pressure. This function reveals information about the superconductor state through the determination of the spectral regions for Cooper-pairs formation. $${D}_{cp}(\omega ,{T}_{c})$$
D
cp
(
ω
,
T
c
)
is built from the well-established Eliashberg spectral function and phonon density of states, calculated by first-principles. $${D}_{cp}(\omega ,{T}_{c})$$
D
cp
(
ω
,
T
c
)
for Nb suggests that the low-frequency vibration region $$\left(\omega <6 \,{\text{meV}}\right)$$
ω
<
6
meV
is where Cooper-pairs are possible. From $${D}_{cp}(\omega ,{T}_{c})$$
D
cp
(
ω
,
T
c
)
, it is possible to obtain the $${N}_{cp}$$
N
cp
parameter, which is proportional to the total number of Cooper-Pairs formed at a temperature $${T}_{c}$$
T
c
. The $${N}_{cp}$$
N
cp
parameter allows an approach to the understanding of the Nb $${T}_{c}$$
T
c
anomalies, measured around 5 and 50 GPa.
“…5 , 6 . By and large, our spectra are in good agreement with previous theoretical reports 12 – 14 . Figure 1 Cooper Pairs Distribution function and Eliashberg function for Niobium under pressure.…”
In this paper, we report Cooper Pairs Distribution function $${D}_{cp}(\omega ,{T}_{c})$$
D
cp
(
ω
,
T
c
)
for bcc Niobium under pressure. This function reveals information about the superconductor state through the determination of the spectral regions for Cooper-pairs formation. $${D}_{cp}(\omega ,{T}_{c})$$
D
cp
(
ω
,
T
c
)
is built from the well-established Eliashberg spectral function and phonon density of states, calculated by first-principles. $${D}_{cp}(\omega ,{T}_{c})$$
D
cp
(
ω
,
T
c
)
for Nb suggests that the low-frequency vibration region $$\left(\omega <6 \,{\text{meV}}\right)$$
ω
<
6
meV
is where Cooper-pairs are possible. From $${D}_{cp}(\omega ,{T}_{c})$$
D
cp
(
ω
,
T
c
)
, it is possible to obtain the $${N}_{cp}$$
N
cp
parameter, which is proportional to the total number of Cooper-Pairs formed at a temperature $${T}_{c}$$
T
c
. The $${N}_{cp}$$
N
cp
parameter allows an approach to the understanding of the Nb $${T}_{c}$$
T
c
anomalies, measured around 5 and 50 GPa.
“…These two competitive factors lead to the temperature-independent behavior of the electronic thermal conductivity. TiN (HfN) holds relatively small electronic thermal conductivity, as 49 W/mK (69 W/mK) at 300 K compared to common metals [41,[43][44][45]. The small electronic thermal conductivity makes the phonon component nonnegligible, shown by the blue ribbons in Fig.…”
Section: A2 Pronounced Effects From Phonon-isotope Scatteringsmentioning
“…Metals such as Cu, silver (Ag), gold (Au), and nickel (Ni) are good candidates owing to superior thermal transport characteristics. 6 Through first-principles calculations, Tong et al 7 and Giri et al 8 found that phonons contribute little to the thermal conductivity of metals and electron− phonon coupling is sensitive to the electronic structure of a metal. Electron−phonon coupling has gained intensive attention in the process of laser manufacturing owing to the strong electron−phonon nonequilibrium (EPN).…”
Section: Introductionmentioning
confidence: 99%
“…Metals such as Cu, silver (Ag), gold (Au), and nickel (Ni) are good candidates owing to superior thermal transport characteristics . Through first-principles calculations, Tong et al and Giri et al found that phonons contribute little to the thermal conductivity of metals and electron–phonon coupling is sensitive to the electronic structure of a metal. Electron–phonon coupling has gained intensive attention in the process of laser manufacturing owing to the strong electron–phonon nonequilibrium (EPN). , With the development of thermometry, electron–phonon interaction (EPI) gradually received attention in noncontact photothermal measurements including Raman spectroscopy and pump–probe spectroscopy. , The same focus of these studies is the time scales of EPI, which are on the order of 1 ps .…”
Electron−phonon interaction (EPI) plays an important role in the transport property of metals. Nevertheless, EPI in polymer nanocomposites containing metal fillers has not been fully investigated due to the complicated physical mechanisms. In this work, the copper−polyethylene (Cu−PE) nanocomposite is used as a model system, and nonequilibrium molecular dynamics (NEMD) simulation combined with the two-temperature model (TTM) is conducted to reveal the role of EPI in Cu−PE systems. The effects of filler length, filler property, and EPI strength on thermal conductivity are revealed. A dimensionless number (Θ) is defined to characterize the electron−phonon nonequilibrium (EPN) degree. The results show that the EPN degree has a significant impact on thermal conductivity. When the system is in a strong EPN state, the effects of EPI on thermal conductivity can be negligible. However, when the EPN degree gradually decreases, ignoring EPI can severely underestimate the thermal conductivity. Furthermore, the temperature profile of electrons and phonons is extracted and the equivalent thermal circuit is presented. The additional thermal resistances induced by the nonlocal and nonequilibrium effects are revealed. Phonon spectra analysis and heat current decomposition are performed to uncover the underlying mechanisms. In addition, the effects of atomic mass density and filler types on thermal conductivity are revealed. Stress− strain simulation is conducted to unravel the effects of strain rates on the mechanical property. The results are useful for designing polymer nanocomposites with controlled thermal conductivity.
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