Temperature-linear Resistivity in Twisted Double Bilayer Graphene

TL;DR

This study investigates how temperature-linear resistivity in twisted double bilayer graphene varies with carrier density, displacement field, and twist angle, revealing phonon scattering and quantum critical behaviors.

Contribution

It provides the first detailed experimental analysis of T-linear resistivity dependence on multiple parameters in TDBG, highlighting phonon scattering and quantum criticality.

Findings

T-linear resistivity observed over wide parameter ranges at large twist angles.

Maximum resistivity slope occurs at phase transition boundary in correlated states.

Evidence of quantum critical behavior and diverging effective mass near critical points.

Abstract

We report an experimental study of carrier density (n), displacement field (D) and twist angle ({\theta}) dependence of temperature (T)-linear resistivity in twisted double bilayer graphene (TDBG). For a large twist angle ({\theta}>1.5{\deg}) where correlated insulating states are absent, we observe a T-linear resistivity (with the slope of the order ~10{\Omega}/K) over a wide range of carrier density and its slope decreases with increasing of n, in agreement with acoustic phonon scattering model semi-quantitatively. The slope of T-linear resistivity is non-monotonically dependent on the displacement field with a single peak structure. For device with {\theta}~1.23{\deg} at which correlated states emerge, the slope of T-linear resistivity is found maximum (~100{\Omega}/K) at the boundary of the halo structure where phase transition occurs, with signatures of continuous phase transition, Planckian dissipation, and the diverging effective mass; these observations are in line with quantum critical behaviors, which might be due to the symmetry-breaking instability at the critical points. Our results shed new light on correlated physics in TDBG and other twisted moir\'e systems.