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arXiv · 2305.09120

The kinetic theory of ultra-subsonic fermion systems and applications to flat band magic angle twisted bilayer graphene

Seth M. Davis·Sankar Das Sarma
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Abstract

The only kinematically-allowed phonon-scattering events for bands of subsonic fermions ($v_F < v_p$) are interband transitions, leading to different low-$T$ transport physics than in the typical supersonic case. We apply a kinetic theory of phonon-limited transport to a generic two-band system of subsonic fermions, deriving formulae for relaxation times and resistivity that are accurate in the limit of close bands and small $v_F/v_p$. We predict regimes of $\rho \propto T$, $\rho \propto T^2$, and perfect conductivity. Our theory predicts linear-in-$T$ resistivity down to a crossover temperature that is suppressed from its supersonic analogue by a factor of $v_F/v_p$, offering a new explanation for low-$T$ "strange metal" behavior observed in flat band systems.

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Seth M. Davis, Sankar Das Sarma. 2023-05-16. The kinetic theory of ultra-subsonic fermion systems and applications to flat band magic angle twisted bilayer graphene. https://doi.org/10.1103/physrevb.109.195105

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