Plasmon Mediation of Charge Pairing in High Temperature Superconductors

A Bose-Einstein condensate (BEC) of a nonzero momentum Cooper pair constitutes a composite boson or simply a boson. We demonstrated that the quantum coherence of the two-component BEC (boson and fermion condensates) is controlled by plasmons. It has been proposed that plasmons, observed in both electron-doped and hole-doped cuprates, originates from the long-range Coulomb screening, where the transfer momentum q ⟶ 0 . We further show that the screening mediates boson-fermion pairing at condensate state. While only about 1 % of plasmon energy mediates the charge pairing, most of the plasmon energy is used to overcome the modes that compete against superconductivity such as phonons, charge density waves, antiferromagnetism, and damping effects. Additionally, the dependence of frequency of plasmons on the material of a superconductor is also explored. This study gives a quantum explanation of the modes that enhance and those that inhibit superconductivity. The study informs the nature of electromagnetic radiations (EMR) that can enhance the critical temperature of such materials.

Holographic colour superconductors at finite coupling with NJL Interactions

We study a bottom-up holographic description of the QCD colour superconducting phase in the presence of higher derivative corrections. We expand this holographic model in the context of Gauss–Bonnet (GB) gravity. The Cooper pair condensate has been investigated in the deconfinement phase for different values of the GB coupling parameter $$\lambda _{G B}$$ λ GB , we observe a change in the value of the critical chemical potential $$\mu _c$$ μ c in comparison to Einstein gravity. We find that $$\mu _c$$ μ c grows as $$\lambda _{G B}$$ λ GB increases. We add four fermion interactions and show that in the presence of these corrections the main interesting features of the model are still present and that the intrinsic attractive interaction can not be switched off. This study suggests to find GB corrections to equation of state of holographic QCD matter.

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

Cooper-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.

Real-time observation of Cooper pair splitting showing strong non-local correlations

Controlled generation and detection of quantum entanglement between spatially separated particles constitute an essential prerequisite both for testing the foundations of quantum mechanics and for realizing future quantum technologies. Splitting of Cooper pairs from a superconductor provides entangled electrons at separate locations. However, experimentally accessing the individual split Cooper pairs constitutes a major unresolved issue as they mix together with electrons from competing processes. Here, we overcome this challenge with the first real-time observation of the splitting of individual Cooper pairs, enabling direct access to the time-resolved statistics of Cooper pair splitting. We determine the correlation statistics arising from two-electron processes and find a pronounced peak that is two orders of magnitude larger than the background. Our experiment thereby allows to unambiguously pinpoint and select split Cooper pairs with 99% fidelity. These results open up an avenue for performing experiments that tap into the spin-entanglement of split Cooper pairs.

The Nuclear Cooper Pair

This monograph presents a unified theory of nuclear structure and nuclear reactions in the language of quantum electrodynamics, Feynman diagrams. It describes how two-nucleon transfer reaction processes can be used as a quantitative tool to interpret experimental findings with the help of computer codes and nuclear field theory. Making use of Cooper pair transfer processes, the theory is applied to the study of pair correlations in both stable and unstable exotic nuclei. Special attention is given to unstable, exotic halo systems, which lie at the forefront of the nuclear physics research being carried out at major laboratories around the world. This volume is distinctive in dealing in both nuclear structure and reactions and benefits from comparing the nuclear field theory with experimental observables, making it a valuable resource for incoming and experienced researchers who are working in nuclear pairing and using transfer reactions to probe them.