Does magic-angle superconductivity require the neighbouring correlated insulator? · revision history

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Revision 1: Does magic-angle superconductivity require the neighbouring correlated insulator
Revision 2: Does magic-angle superconductivity require the neighbouring correlated insulator?
Plain
Superconductivity in magic-angle graphene appears next to insulating states, as in cuprates, but devices in which a nearby metal gate screens the electron repulsion lose the insulators and keep the superconductivity, so the two may have different causes.
Precise
Saito et al. (Nature Physics 16, 926, 2020, arXiv:1911.13302) and Stepanov et al. (Nature 583, 2020, doi:10.1038/s41586-020-2459-6) found superconductivity in twisted bilayer graphene without correlated insulators at $\nu = \pm2$, for twist angles detuned from 1.1 deg or with metallic gates a few nm away. Determine whether the superconductor and the correlated insulator share an origin (pairing from doping the ordered insulator) or compete for the same flat-band electrons. An answer is the dependence of $T_{c}$ and of the insulating gap on gate-screening length $d$ and twist angle, with the pairing state shown to be the same or different with and without the insulator.
Settled by
$T_c$, insulating-gap and gap-symmetry measurements in devices with gate distance $d$ varied from about 1 to 50 nm at fixed twist angle and strain.
Kind
well-posed
Answer type
yes-no
References
(empty)
Literature status
partially-resolved
Status note
2020 screening experiments showed superconductivity can exist without the insulators; whether both share one pairing mechanism remains unsettled as of 2026.
Posed since
2018

Decisions