PIRSA:22100095

On the Electron Pairing Mechanism of Copper-Oxide High Temperature Superconductivity

Davis, S. (2022). On the Electron Pairing Mechanism of Copper-Oxide High Temperature Superconductivity. Perimeter Institute. https://pirsa.org/22100095

Davis, Seamus. On the Electron Pairing Mechanism of Copper-Oxide High Temperature Superconductivity. Perimeter Institute, Oct. 12, 2022, https://pirsa.org/22100095 

          @misc{ pirsa_PIRSA:22100095,
            doi = {10.48660/22100095},
            url = {https://pirsa.org/22100095},
            author = {Davis, Seamus},
            keywords = {Other},
            language = {en},
            title = {On the Electron Pairing Mechanism of  Copper-Oxide High Temperature Superconductivity},
            publisher = {Perimeter Institute},
            year = {2022},
            month = {oct},
            note = {PIRSA:22100095 see, \url{https://pirsa.org}}
          }

Seamus Davis

Cornell University

Talk number
PIRSA:22100095
Collection
Talk Type
Subject
Abstract

The elementary CuO2 plane sustaining cuprate high temperature superconductivity occurs typically at the base of a periodic array of edge-sharing CuO5 pyramids. Virtual transitions of electrons between adjacent planar Cu and O atoms, occurring at a rate t/ℏ and across the charge-transfer energy gap E, generate ‘superexchange’ spin-spin interactions of energy J≈4t4/E3 in an antiferromagnetic correlated-insulator state. However, hole doping this CuO2 plane converts this into a very high temperature superconducting state whose electron-pairing is exceptional. A leading proposal for the mechanism of this intense electron-pairing is that, while hole doping destroys magnetic order it preserves pair-forming superexchange interactions governed by the charge-transfer energy scale E.

To explore this hypothesis directly at atomic-scale, we developed high-voltage single-electron and electron-pair (Josephson) scanning tunneling microscopy, to visualize the interplay of E and the electron-pair density nP in Bi2Sr2CaCu2O8+x. Changing the distance δ between each pyramid’s apical O atom and the CuO2 plane below, should alter the energy levels of the planar Cu and O orbitals and thus vary E.  Hence, the responses of both E and nP to alterations in δ that occur naturally in Bi2Sr2CaCu2O8+x were visualized. These data revealed, directly at atomic scale, the crux of strongly correlated superconductivity in CuO2: the response of the electron-pair condensate to varying the charge transfer energy. Strong concurrence between these observations and recent three-band Hubbard model DMFT predictions for superconductivity in hole-doped Bi2Sr2CaCu2O8+x (PNAS 118, e2106476118 (2021)) indicate that charge-transfer superexchange is the electron-pairing mechanism (PNAS 119, 2207449119 (2022)).

Zoom link:  https://pitp.zoom.us/j/95592484157?pwd=YU56Wno3WnBIUTlyaC9VSHJ3cGxZUT09