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Physics Colloquium 293 (9/15/17)

September 15, 2017 - 10:30am

Marco Bernardi, Ph.D., California Institute of Technology


Calculations of charge transport and ultrafast dynamics have relied on heuristic approaches for the past several decades. Recent progress in combining density functional theory and related methods with kinetic equations, such as the Boltzmann transport equation (BTE), are enabling spectacular advances in computing carrier dynamics in materials from first principles. A special role is played by the interaction between charge carriers and lattice vibrations, also known as the electron-phonon (e-ph) interaction, which dominates carrier dynamics at room temperature and for carrier energies within a few eV of the band edges. We will discuss our recently developed methods to compute and interpolate e-ph scattering processes on ultra-fine Brillouin zone grids, and then show how these developments enable new computations of charge transport and ultrafast dynamics, including: 

1) Accurate calculations of the carrier mobility in polar semiconductors [ 1] and oxides, including new methods to treat complex materials with structural phase transitions (e.g., perovskites) and new insight into charge transport in organic molecules.
2) The ultrafast dynamics and detailed scattering mechanisms of excited (so-called “hot” ) carriers. We will discuss the application of this framework to solar energy conversion, the interpretation of ultrafast spectroscopy results, and open problems in gallium nitride light emission technologies. A new parallel algorithm to propagate in time the BTE [2] will be introduced.
J.-J. Zhou and M. Bernardi Phys. Rev. B (Rapid Commun.) 94, 201201 (2016). 
V. Jhalani, J.-J. Zhou and M. Bernardi Nano Letters 17, 5012 (2017).


Contact Information

David Strubbe
Assistant Professor
5200 North Lake Rd.
Merced, CA 95343
United States