Kavli Affiliate: Debanjan Chowdhury
| First 5 Authors: Omri Lesser, Sagnik Banerjee, Xuepeng Wang, Jaewon Kim, Ehud Altman
| Summary:
It is well known that disorder can induce low-energy Andreev bound states in
a sign-changing, but fully gapped, superconductor at $pi-$junctions.
Generically, these excitations are localized. Starting from a superconductor
with a sign-changing and nodeless order parameter in the clean limit, here we
demonstrate a mechanism for increasing the localization length associated with
the low-energy Andreev bound states at a fixed disorder strength. We find that
the Fubini-Study metric associated with the electronic Bloch wavefunctions
controls the localization length and the hybridization between bound states
localized at distinct $pi-$junctions. We present results for the inverse
participation ratio, superfluid stiffness, site-resolved and disorder-averaged
spectral functions as a function of increasing Fubini-Study metric, which
indicate an increased tendency towards delocalization. The low-energy
properties resemble those of a dirty nodal superconductor with gapless
Bogoliubov excitations. We place these results in the context of recent
experiments in moire graphene superconductors.
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