Conductivity of an electron coupled to anharmonic phonons

Abstract

We study the impact of phonon anharmonicity on the electronic dynamics of soft materials using a nonperturbative quantum-classical approach. The method is applied to a one-dimensional model of doped organic semiconductors with low-frequency intermolecular lattice phonons. We find that anharmonicity that leads to phonon hardening increases the mobility and anharmonicity that leads to phonon softening decreases the mobility. We also test various approximations, including the use of adiabatic phonon disorder, an effective harmonic model with temperature-dependent frequencies, and the Boltzmann transport equation with second-order perturbation theory scattering rates. Overall, we find surprisingly good agreement between all methods but that accounting for phonon anharmonicity is important for accurate prediction of electronic transport including both quantitative mobility values and their qualitative temperature dependence. For the model studied, phonon lifetime effects have relatively little impact on carrier transport, but the effective frequency shift due to anharmonicity is essential. In cases with highly asymmetric, non-Gaussian disorder, an effective harmonic model cannot quantitatively reproduce mobilities or finite-frequency conductivity, and this is especially true for acoustic phonons.

References in corpus (5)

• Entropy driven stabilization of energetically unstable crystal structures explained from first principles theory
• First-principles dynamics of electrons and phonons
• Linear and nonlinear spectroscopy from quantum master equations
• Anharmonic Lattice Vibrations in Small-Molecule Organic Semiconductors
• Crossover from Super- to Sub-Diffusive Motion and Memory Effects in Crystalline Organic Semiconductors

Cited by in corpus (5)

• Charge transport limited by nonlocal electron-phonon interaction. II. Numerically exact quantum dynamics in the slow-phonon regime
• Strong anharmonicity dictates ultralow thermal conductivities of type-I clathrates
• Dissecting Exciton-Polariton Transport in Organic Molecular Crystals: Emerging Conductivity Assisted by Intermolecular Vibrational Coupling
• Numerically "exact" charge transport dynamics in a dissipative electron-phonon model rationalizing the success of the transient localization scenario
• Quantum-classical study of charge transport in organic semiconductors with multiple low-frequency vibrational modes