Broad Band Mott Localization Theory for Hot LK99 Superconductivity

Channai and Canadian researchers presented a theory for LK99 superconductivity. They have presented a couple of scenarios, keeping solid state and quantum chemical constraints in mind and suggested possibility of hot superconductivity via electronic mechanism of doped Spin 1/2 Mott insulator, utilizing broad band Mott localization.

Their theory makes use of doped spin- 1/2 doped Mott insulator route to superconductivity, with the emphasis on the fact that monovalent metal atoms under suitable conditions (such as reduced dimensions) readily undergo Mott localization. Over years they have used this AMI idea to develop tangible models to understand superconductivity in complex solid state systems such as hydrides, K3p-Terphenyl, B-doped diamond and Ag-Au nanostructures, doped graphene and silicene.

They propose a scenario, without full justification from quantum chemical calculations etc. They briefly discuss possibility of a related, but somewhat different scenario. Here Cu atom get accommodated as a neutral impurity and creates an s-like donor impurity state in the band gap of Pb10(PO4)6O . As impurity concentration is increased impurity state wave function will overlap and they could have a Anderson-Mott insulator to superconductor transition, as outlined in our theory for B doped diamond. The binding energy of the donor state could in principle get Tc reaching the scales claimed.

As a key idea and notion, superconductivity in doped Mott insulators began while attempting to understand high Tc cuprates by Anderson in 1987. It is becoming increasingly clear that this idea has a wide applicability.

They suggest experimental exploration of the rich field of low dimensional monovalent metals, monovalent metal doped minerals, insulators and in metallurgy, where variety of nanostructures are norm of the day.

While Cu2+ doping is an attractive idea, correponding isolated bare band widths are so low that Cooper pairs will get localized strongly by
lattice distortion and disorder. For the scale of reported Tc, we need broad band Mott localization rather than narrow band Mott localization. It is important to recall that even in high Tc cuprates an effective single band (which is not isolated) width is of the order of 2 eV, which is capable of giving superconductivity. at temperatures close to 100 K.

Arxiv – Broad Band Mott Localization is all you need for Hot Superconductivity: Atom Mott Insulator Theory for Cu-Pb Apatite

Abstract

A hypothetical non-dimerized Cu chain in equilibrium is a spin-\half atom Mott insulator (AMI), eventhough its band width is high ~ 10 eV. This RVB reservoir has a large exchange coupling J ~ 2 eV. This idea of, \textit{broad band Mott localization} was used by us in our earlier works, including prediction of high Tc superconductivity in doped graphene, silicene and a theory for hot superconductivity reported in Ag-Au nanostructures (TP 2008). In the present work we identify possible random AMI subsystems in Cu-Pb Apatite and develop a model for reported hot superconductivity (LKK 2023). In apatite structure, network of interstitial columnar spaces run parallel to c-axis and ab-plane. They accomodate excess copper, as neutral Cu atom clusters, chains and planar segments. They are our emergent AMI’s. Electron transfer from AMI’s to insulating host, generates strong local superconducting correlation, via phyics of doped Mott insulator. Josephson coupling between doped AMI’s, establishes hot superconductivity. A major Challenge to superconducting order in real material is competing insulating phases – valence bond solid (spin-Peirels)-lattice distortions etc. AMI theory points to ways of making the \textit{elusive superconductivity} palpable. We recommend exploration of hot superconductivity in the rich world of minerals and insulators, via metal atom inclusion.