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Condensed Matter Seminar - "On the Electron Pairing Mechanism of Copper-Oxide High Temperature Superconductivity"

Event Type
Seminar/Symposium
Sponsor
Physics - Condensed Matter
Location
via Zoom
Virtual
wifi event
Date
Nov 19, 2021   1:00 pm  
Speaker
Seamus Davis, University of Oxford - University College Cork - Cornell University.
Contact
Stephen Bullwinkel
E-Mail
bullwink@illinois.edu
Phone
217-333-1652
Views
79
Originating Calendar
Physics - Condensed Matter Seminar

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 ε,  generate ‘superexchange’ spin-spin interactions of energy J≈4t43 in an antiferromagnetic correlated-insulator state. However, hole doping this CuOplane 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 ε. To explore this hypothesis directly at atomic-scale, we combine single-electron and electron-pair (Josephson) scanning tunneling microscopy to visualize both ε and the electron-pair density ns, in Bi2Sr2CaCu2O8+x.  The responses of both ε and ns to alterations in the distance δ between planar Cu and apical O atoms are thus visualized. These data reveal the long-sought crux of microscopic theory for cuprate  superconductivity, the response of condensate electron-pair density ns to varying the charge transfer energy  ε. Concurrence of predictions from strong-coupling theory for hole-doped charge-transfer insulators with these observations, indicates that charge-transfer superexchange is the electron-pairing mechanism of superconductive Bi2Sr2CaCu2O8+x.

 

Zoom link will be forwarded to Condensed Matter Seminar email list. For a copy of the link or to be added to the email list, please contact Stephen Bullwinkel (bullwink@illinois.edu).

Recordings of Condensed Matter Seminar events can be found on mediaspace: https://mediaspace.illinois.edu/channel/Condensed%2BMatter%2BSeminar%2BTalks%2BFall%2B2021/234020562 

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