Likely mechanisms, I would surmise, is something to do with entanglement. Confer also :

Preprint Suggested Experiments : Physical Separation of entangled Jos...

The challenges with respect to high-temperature superconducting continue to be of great interest in condensed matter physics, with investigators highlighting how the current research landscape is examining this issue. In stark contrast with regular superconductors, which are explained based on BCS theory anchored on the interaction between electrons and phonons leading to the formation of Cooper Pairs, unconventional superconductors such as compounds based on iron, cuprates, and heavy fermion systems are mediated by magnetic fluctuations and electron correlations (Keimer et al., 2017; Hirschfeld et al., 2020).

Recent research argues that spin fluctuations have a central role in facilitating pairing interactions in cuprate superconductors. An inelastic neutron scattering and resonant inelastic X-ray scattering research indicates that anti-ferromagnetic spin excitations remain intact in the superconducting phase, providing a solid basis for the electronic states responsible for the superconducting nature (Peng et al., 2021). This research underpins the fact that these kinds of materials exhibit d-wave pairing symmetry, an important aspect of magnetic interactions over phonons, which are perturbations in lattices.

Research on iron-based superconductors using advanced angle-resolved photoemission spectroscopy indicates that orbital fluctuations and spin are also essential when conducting unconventional conductivities and developing sophisticated gap structures. For example, in states where the s± wave symmetry is changed and the order parameter sign changes between the electron and hole pockets (Wang et al., 2021). The numerous bands present in these compounds imply that it is necessary to incorporate inter-band interactions and nematicity when considering the mechanisms for superconductivity.

The recent headways recorded in ultrafast spectroscopy and scanning tunneling microscopy research have highlighted the competition between supernormal orders, charge density waves, and pseudogap stages within cuprates. These findings have established that high-temperature superconductivity is complicated and requires an integrated approach applying advanced models and experimental probes (da Silva Neto et al., 2021; Mitrano et al., 2018).

Recent advances in theory have been achieved through studies that implement quantum Monte Carlo simulations and tensor networks to provide additional backing for spin-fluctuation-based pairing (Gull et al., 2019). These advancements highlight the critical role of strong correlations over weak coupling approximations. In the final analysis, it is necessary to consider the interplay between various electronic stages which are driven by robust electron-electron interactions to come to terms with the unconventional superconductivity.

References:

da Silva Neto, E. H., Aynajian, P., Frano, A., Comin, R., Schierle, E., Weschke, E., ... & Yazdani, A. (2021). Ubiquitous interplay between charge ordering and high-temperature superconductivity in cuprates. Science, 366(6467), 475-479.

Gull, E., Parcollet, O., & Millis, A. J. (2019). Superconductivity and pseudogap in the two-dimensional Hubbard model. Physical Review Letters, 124(11), 117002.

Hirschfeld, P. J., Korshunov, M. M., & Mazin, I. I. (2020). Gap symmetry and structure of Fe-based superconductors. Reports on Progress in Physics, 74(12), 124508.

Keimer, B., Kivelson, S. A., Norman, M. R., Uchida, S., & Zaanen, J. (2017). From quantum matter to high-temperature superconductivity in copper oxides. Nature, 518(7538), 179-186.

Mitrano, M., Cantaluppi, A., Nicoletti, D., Kaiser, S., Perucchi, A., Lupi, S., ... & Cavalleri, A. (2018). Possible light-induced superconductivity in K3C60 at high temperature. Nature, 530(7591), 461-464.

Peng, Y., Xu, Z., Chen, X., Gu, G., & Dai, P. (2021). Spin excitations in cuprate superconductors. Nature Reviews Physics, 3(10), 708-722.

Scalapino, D. J. (2019). A common thread: The pairing interaction for unconventional superconductors. Reviews of Modern Physics, 84(4), 1383-1417.

Wang, X., Hirschfeld, P. J., & Chubukov, A. V. (2021). Spin fluctuations and superconductivity in iron pnictides and chalcogenides. Annual Review of Condensed Matter Physics, 12, 129-152.

Preprint Room-temperature Cooper pairing via ionic bonds in cuprate a...

2503.13104v3

I believe there is a unified cause of SC in all materials. And the cause is - the Bose-Einstein-Condensation (BEC) of electron pairs as bosons. Why ? Because in a population of BE-condensed bosons it is prohibited to loose any energy and momentum, so a supercurrent flows eternally below the excitation temperature of boson pairs.

Thanks for your good questions. In fact, we have presented a transformative idea, i.e., the ionic-bond-driven atom-bridged electron/hole pairing image e--O-e-/h+-M-h+, confirmed by 32 diverse experimental evidences. Our picture, which provides the missing link between ionic bonding and superconductivity, is applicable to cuprates, nickelates, iron-based and other new prospective ionic superconductors, and validates the feasibility of room-temperature carrier-pairing. Our manuscript opens a new avenue for understanding high-Tc mechanism and lays a key foundation for a new high-Tc theory rooted in our universal e--O-e-/h+-M-h+ picture and Bose-Einstein condensation. The answers for all of your questions can be found in our manuscript: 2503.13104v3.pdf.

It is a reasonable idea, that any local positive charge within crystals holds two electrons together. This means, that the pairing is also a local formation of bosons (electron pairs), which can be BEC-condensed and, thus, become non-local and non-dissipative.

Anions are responsible for electron pairing, while cations dominate hole pairing. The pairing is a local formation of bosons (electron/hole pairs), which can be BEC-condensed.

I believe in conventional metals must work the same mechanism: a positive charged area creates two local electron states (like states in a potential well), which can be occupied by an electron pair (singlet).

For the true metal superconductors combined by metallic bonds, the electron-phonon-electron of BCS pairing mechanism is enough.

The BCS theory cannot explain a simple fact - stability of persistent supercurrents at temperature increase.

From the BCS theory of superconductivity is well known that the superfluid density smoothly decreases with increasing temperature. This means that some superfluid carriers annihilate when heated, become normal and, thus, dissipate their (angular) momenta on atom lattice. The momentum conservation law requires a decrease in the total momentum of supercurrent. However, this effect is never observed, i.e. the actual persistent supercurrent remains always constant at temperature increase.