Quantifying the Charge Carrier Interaction in Metallic Twisted Bilayer Graphene Superlattices

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid-State Physics

Background:

• The dominant charge carrier interaction mechanism in twisted bilayer graphene (TBG) is debated, with proposed roles for electron-phonon, electron-electron, and electron-magnon interactions.
• The Bloch-Grüneisen equation provides a theoretical framework relating resistivity to interaction mechanisms via a power-law exponent (p).

Purpose of the Study:

• To resolve the ambiguity in charge carrier interaction mechanisms in TBG.
• To analyze temperature-dependent resistivity in TBG by generalizing the Bloch-Grüneisen equation.
• To investigate the influence of Moiré superlattice constant and charge carrier concentration on these interactions.

Main Methods:

• Generalization of the Bloch-Grüneisen equation to treat the power-law exponent (p) as a free-fitting parameter.
• Fitting experimental resistivity data of TBG to the generalized Bloch-Grüneisen equation.
• Analysis of the extracted p-values in relation to Moiré superlattice constant (λ) and charge carrier concentration (n).

Main Results:

• The study found that the power-law exponent (p) in TBG is not fixed but varies smoothly between 1.4 and 4.4.
• These p-values depend on the Moiré superlattice constant (λ) and charge carrier concentration (n).
• Observed linear temperature-dependent resistance in TBG is interpreted as p approaching 1, indicating quasielastic charge interaction with acoustic phonons.

Conclusions:

• Different charge carrier interaction mechanisms in TBG superlattices exhibit a smooth transition rather than a single dominant mechanism.
• The generalized Bloch-Grüneisen equation provides a versatile tool for analyzing complex interactions in materials.
• The findings have implications for understanding phenomena in superconductivity and geology.