mat-epw-mobility

mat-epw-mobility

Goal

To compute the intrinsic phonon-limited carrier mobility $\mu(T)$ of a 2D semiconductor in the Self-Energy Relaxation Time Approximation (SERTA), together with the mode-resolved electron-phonon coupling matrix elements $|g(k, q, \nu)|$, from first principles using the Quantum ESPRESSO + EPW pipeline. The route interpolates the electron-phonon vertex onto dense fine grids via maximally localized Wannier functions and applies the 2D Frohlich long-range kernel needed for polar monolayers.

Background

Carrier mobility limited by phonon scattering requires the electron-phonon matrix elements $g_{mn\nu}(k, q)$ on grids far denser than any tractable DFPT calculation. EPW solves this by computing $g$ on a coarse q-grid with DFPT, transforming to a maximally localized Wannier basis, and interpolating to fine k/q meshes. For 2D polar materials, the long-range Frohlich part of $g$ diverges as $1/q$ near the zone centre and must be treated with a 2D-truncated Coulomb kernel (lpolar, system_2d), otherwise $\mu$ collapses by a factor of ~3.

Unlike the DFT+AMSET route in mat-dft-electronic-transport, which uses a momentum-relaxation-time approximation on VASP band structures, this skill computes the full first-principles electron-phonon vertex. It is complementary to mat-dft-electron-phonon (which targets temperature-dependent bandgap renormalization) and to mat-phonon (MLIP phonons).

The pipeline is a DAG. Steps 3 and 5 are optional (a standalone dielectric check and a DFPT $|g|$ benchmark); the transport path is 1 -> 2 -> 4 -> 6 -> 7 -> 9.

                       1 SCF
           +-------------+--------------+
           v             v              v
      3 DFPT-Gamma   4 DFPT          2 NSCF
      (eps_inf, Z*)  uniform-q       (explicit k)
      (optional)         |               |
                         v               |
                    6 pp.py gather       |
                         |    \          |
                         |     v         v
                         |   7 Wannierize
                         |     |     |
                         v     v     v
                    9 EPW    8 EPW  (8 also <- 5 DFPT single-q
                    SERTA    prtgkk      benchmark, optional)
                    mu(T)    |g|