▎ 摘 要
We have carried out a theoretical investigation of hot electron power loss P, involving electron-acoustic phonon interaction, as a function of twist angle theta, electron temperature T-e and electron density n(s) in twisted bilayer graphene. It is found that as theta decreases closer to magic angle theta(m), P enhances strongly and theta acts as an important tunable parameter, apart from T-e and n(s). In the range of T-e = 1-50 K, this enhancement is similar to 250-450 times the P in monolayer graphene (MLG), which is manifestation of the great suppression of Fermi velocity v(F)* of electrons in moire flat band. As theta increases away from theta(m), the impact of theta on P decreases, tending to that of MLG at theta similar to 3 degrees. In the Bloch-Gruneisen (BG) regime, P similar to T-e(4), n(s)(-1/2) and v(F)(*-2). In the higher temperature region (similar to 10-50 K), P similar to T-e(delta), with delta similar to 2.0, and the behavior is still super linear in T-e, unlike the phonon limited linear-in-T (lattice temperature) resistivity rho(p). P is weakly, decreasing (increasing) with increasing n(s) at lower (higher) T-e, as found in MLG. The energy relaxation time tau(e) is also discussed as a function of theta and T-e. Expressing the power loss P = F-e(T-e) - F-e(T), in the BG regime, we have obtained a simple and useful relation F-e(T)mu(p)(T) = (ev(s)(2)/2) i.e. F-e(T) = (n(s)e(2)v(s)(2)/2)rho(p), where mu(p) is the acoustic phonon limited mobility and v(s) is the acoustic phonon velocity. The rho(p) estimated from this relation using our calculated F-e(T) is nearly agreeing with the rho(p) of Wu et al (2019 Phys. Rev. B 99 165112).