Unconventional superconductivity in magic-strain graphene superlattices

TL;DR

This paper introduces the concept of magic-strain in graphene, demonstrating how mechanical relaxation can induce unconventional superconductivity and insulating states, offering a new tunable platform for correlated electronic phenomena.

Contribution

It presents the novel idea of magic-strain in graphene systems and explores its effects on superconductivity and insulator transitions beyond traditional twisting methods.

Findings

Strain-induced superconductivity with ultra-flat bands.

Semimetal-insulator transition with a 0.39 eV gap.

Strain as a practical tuning parameter for electronic phases.

Abstract

Extensive investigations on the Moir\'e magic-angle have been conducted in twisted bilayer graphene, unlocking the mystery of unconventional superconductivity and insulating states. In analog to magic angle, here we demonstrate the new concept of magic-strain in graphene systems by judiciously tailoring mechanical relaxation (stretch and compression) which is easier to implement in practice. We elucidate the interplay of strain-induced effects and delve into the resulting unconventional superconductivity or semimetal-insulator transition in relaxation-strained graphene, going beyond the traditional twisting approach. Our findings reveal how relaxation strain can trigger superconducting transitions (with an ultra-flat band at the Fermi level) or the semimetal-insulator transition (with a gap opening at the $K$ point of $0.39\rm{~eV}$) in both monolayer and bilayer graphene. These discoveries open up a new branch for correlated phenomena and provide deeper insights into the underlying physics of superconductors, which positions graphene as a highly tunable platform for novel electronic applications.