Charge-4e Superconductivity from Multicomponent Nematic Pairing: Application to Twisted Bilayer Graphene

Area of Science:

• Condensed Matter Physics
• Superconductivity Theory
• Materials Science

Background:

• Unconventional superconductors with multicomponent order parameters exhibit complex electronic phases.
• Lattices with three- and sixfold rotational symmetries are key to understanding exotic superconducting states.

Purpose of the Study:

• To investigate the existence and properties of a charge-4e vestigial superconducting phase above the critical temperature (Tc).
• To explore the competition between the charge-4e state and a vestigial nematic state.
• To identify promising material platforms for realizing these novel superconducting phases.

Main Methods:

• Ginzburg-Landau theory analysis revealing a hidden discrete symmetry.
• Investigating the impact of random strain on competing phases.
• Theoretical modeling of unconventional nematic superconductors.

Main Results:

• A charge-4e vestigial superconducting phase, a condensate of four-electron bound states, exists above Tc.
• This charge-4e state is nearly degenerate with a competing, nonsuperconducting vestigial nematic state.
• Random strain favors the charge-4e state over the nematic phase.

Conclusions:

• The findings are robust due to a hidden discrete symmetry in the Ginzburg-Landau theory.
• Two-dimensional inhomogeneous systems with nematic superconductivity, like twisted bilayer graphene, are promising platforms for the charge-4e phase.
• This work paves the way for realizing elusive charge-4e superconducting states.