Temperature dependence of conductivity and mobility and electro-phonon coupling strength in graphene determined from electron relaxation rates

We report the determination of the electron–phonon coupling strength extracted from the relaxation rates of the electrons’ energy using ultrafast pump–probe spectroscopy. The energy transferred from electrons to the lattice depends on the coupling strength between the two subsystems and the temperatures of electrons and lattice, as described by the two-temperature model. Allen’s theory related the relaxation time to electronic temperature Te and the coupling strength λ⟨ωn⟩ (the second moment of the Eliashberg function). We found the dimensionless parameter λ = (1.36 ± 0.13) × 10−2, which agrees with previous studies, and the deformation potential of the Eg mode 6.4 eV/Å, which is consistent with the value given by Castro Neto and Guinea, Phys. Rev. B 75, 045404 (2007).