Multicomponent Electron-Hole Superfluidity and the BCS-BEC Crossover in Double Bilayer Graphene

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Phenomena

Background:

• Bilayer graphene exhibits unique electronic properties due to its coupled conduction and valence bands.
• Superfluidity, a quantum mechanical phenomenon, is being explored in novel material systems.

Purpose of the Study:

• To investigate the multicomponent superfluid crossover properties in coupled electron-hole sheets of bilayer graphene.
• To determine the influence of tunable carrier densities and energy band gap (E$_{g}$) on superfluidity.
• To identify conditions favorable for achieving high-temperature superconductivity (high-T$_{c}$).

Main Methods:

• Theoretical investigation of superfluid crossover properties.
• Analysis of the impact of varying carrier densities and energy band gaps.
• Modeling of interactions between conduction and valence bands.

Main Results:

• Superfluidity in bilayer graphene is predicted to be multicomponent.
• Small band gaps can enhance superfluid gaps but may hinder Bose-Einstein condensate (BEC) formation at low densities.
• A specific band gap range (E$_{g}$∼80-120 meV) at higher densities facilitates entry into the strong-pairing multiband BCS-BEC crossover regime.

Conclusions:

• The study identifies a critical band gap range for realizing strong-pairing superfluidity in bilayer graphene.
• These findings suggest a pathway towards achieving high-T$_{c}$ superfluidity in this material system.
• Tunable parameters offer a method to control and optimize superfluid properties.