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Séminaire nanostructures et systèmes quantiques

Electron-phonon coupling and transport properties from first principles : what can be done, and what can’t be done yet - Jelena Sjakste - Mardi 19 février 2013 à 11 h

Jelena Sjakste, Laboratoire des Solides Irradies, Ecole Polytechnique, Palaiseau
Mardi 19 février 2013 à 11 h, INSP, couloir 22-32, 2e étage, 201

Electron-phonon coupling is well known as a limiting factor of the electrical charge transport. From the theoretical point of view, it is important to be able to predict various transport properties without resorting to adjustable parameters.

Recently, we developed from-first-principles description of phonon-induced scattering of electrons excited in the conduction band of bulk semiconductors1. Electron-phonon matrix elements turn out to be a crucial ingredient, whose neglect prevents a correct understanding of which phonons are responsible for the electronic scattering and estimation of the electron-phonon contribution to stability of electronic levels1,2,3. For example, in the case of impurity states in doped silicon, the complex behaviour of the electron-phonon matrix elements determines the fact that the effect of the electron-phonon scattering on the stability of impurity levels is much smaller than what was previously believed for 50 years22.

Moreover, despite great advances in predicting the electronic structure of materials, the ability to compute thermoelectric transport properties from first principles is still unrealized in general, even for simple bulk materials. Recently, in collaboration with a group of N. Mingo (Grenoble, France), we combined our ab initio data for electronic structure and electron-phonon scattering matrix elements with Boltzmann solver for transport coefficients4. The thermoelectric coefficients obtained with our method are in excellent agreement with experiment. This approach permitted us to reduce the number of ad hoc parameters in calculation of transport coefficients.

In this seminar, I will address our recent work on electron-phonon coupling with density-functional based methods. In more general way, I will briefly review the possibilities offered by DFT to predict structural, electronic, vibrational and transport properties of materials.

1 J. Sjakste, N. Vast, V. Tyuterev, Phys. Rev. Lett. 99 (2007).
2 V. Tyuterev, J. Sjakste, N. Vast, Phys. Rev. B 81 (2010) 245212.
3 V. G. Tyuterev, S. V. Obukhov, N. Vast, and J. Sjakste, Phys. Rev. B 84 (2011) 035201.
4 Z. Wang, S. Wang, S. Obukhov, N. Vast, J. Sjakste, V. Tyuterev, N. Mingo, Phys. Rev. B 83 (2011) 205208.