scholarly journals Cooper Pairs Distribution function for bcc Niobium under pressure from first-principles

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
G. I. González-Pedreros ◽  
J. A. Camargo-Martínez ◽  
F. Mesa
Keyword(s):  
Distribution Function ◽  
Density Of States ◽  
First Principles ◽  
Low Frequency ◽  
Cooper Pairs ◽  
Phonon Density ◽  
Phonon Density Of States ◽  
Low Frequency Vibration ◽  
Eliashberg Spectral Function

AbstractIn 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.

scholarly journals Cooper-pair distribution function $$D_{cp}(\omega ,T_c)$$ for superconducting $$\hbox {D}_3\hbox {S}$$ and $$\hbox {H}_3\hbox {S}$$

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
G. I. González-Pedreros ◽  
J. A. Camargo-Martínez ◽  
F. Mesa
Keyword(s):  
Distribution Function ◽  
Pair Distribution Function ◽  
Cooper Pair ◽  
Sulfur Isotopes ◽  
Low Frequency ◽  
Cooper Pairs ◽  
Simple Variation ◽  
Theoretical Proposal ◽  
Eliashberg Spectral Function

AbstractCooper-pair distribution function, $$D_{cp}(\omega ,T_c)$$ D cp ( ω , T c ) , is a recent theoretical proposal that reveals information about the superconductor state through the determination of the spectral regions where Cooper pairs are formed. This is built from the well-established Eliashberg spectral function and phonon density of states, calculated by first-principles. From this function is possible to obtain the $$N_{cp}$$ N cp parameter, which is proportional to the total number of Cooper pairs formed at a critical temperature $$T_c$$ T c . Herein, we reported $$D_{cp}(\omega ,T_c)$$ D cp ( ω , T c ) function of the compressed $$D_3S$$ D 3 S and $$H_3S$$ H 3 S high-$$T_c$$ T c conventional superconductors, including the effect of stable sulfur isotopes in $$H_3S$$ H 3 S . $$D_{cp}(\omega ,T_c)$$ D cp ( ω , T c ) suggests that the vibration energy range of 10–70 meV is where the Cooper pairs are possible for these superconductors, pointing out the possible importance of the low-energy region on the electron–phonon superconductivity. This has been confirmed by the fact that a simple variation in the low-frequency region induced for the substitution of S atoms in $$H_3S$$ H 3 S by its stable isotopes can lead to important changes in $$T_c$$ T c . The results also show proportionality between $$N_{cp}$$ N cp parameter and experimental or theoretical $$T_c$$ T c values.

Direct determination of the phonon density of states inβ−Sn

2000 ◽  
Vol 61 (22) ◽  
pp. R14881-R14884 ◽  
Author(s):  
A. Barla ◽  
R. Rüffer ◽  
A. I. Chumakov ◽  
J. Metge ◽  
J. Plessel ◽  
...  
Keyword(s):  
Density Of States ◽  
Direct Determination ◽  
Phonon Density ◽  
Phonon Density Of States

PHONON BEHAVIOR OF Y-Ba-Cu-O SUPERCONDUCTOR AND SEMICONDUCTOR

1987 ◽  
Vol 01 (02) ◽  
pp. 409-412 ◽  
Author(s):  
Jinghui Ruan ◽  
Jizhou Li ◽  
Ansun Yu ◽  
Shu Gan ◽  
Tonghua Yang ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Density Of States ◽  
High Frequency ◽  
Superconducting Transition Temperature ◽  
Low Frequency ◽  
Scattering Method ◽  
Phonon Density ◽  
Superconducting Transition ◽  
Phonon Density Of States ◽  
Neutron Inelastic Scattering

The generalized phonon density of states of Y-Ba-Cu-O superconductor and semiconductor has been measured by neutron inelastic scattering method. The results show that the decrease or disappearance of high frequency modes and the increase of low frequency modes may have some relations to the high superconducting transition temperature

Phonon density of states of model ferroelectrics

2010 ◽  
Vol 1262 ◽  
Author(s):  
Narayani Choudhury ◽  
Alexander I Kolesnikov ◽  
Helmut Schober ◽  
Eric J Walter ◽  
Mark Johnson ◽  
...  
Keyword(s):  
Density Of States ◽  
First Principles ◽  
Density Functional ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Cubic Phase ◽  
Phonon Density ◽  
Phonon Density Of States ◽  
Phonon Spectra ◽  
Quantum Paraelectric

AbstractFirst principles density functional calculations and inelastic neutron scattering measurements have been used to study the variations of the phonon density of states of PbTiO3 and SrTiO3 as a function of temperature. The phonon spectra of the quantum paraelectric SrTiO3 is found to be fundamentally distinct from those of ferroelectric PbTiO3 and BaTiO3. SrTiO3 has a large 70-90 meV phonon band-gap in both the low temperature antiferrodistortive tetragonal phase and in the high temperature cubic phase.Key bonding changes in these perovskites lead to spectacular differences in their observed phonon density of states.

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