Quantum transport

Multiscale models of electron and phonon transport

Electronic and thermal conductivities govern the performance of thermoelectrics, electronics, photovoltaics and many other technologies. Ab-initio predictions of electron and phonon transport and coupling are complicated by the need to capture the multiscale dynamics and scattering of elementary excitations that cannot be explicitly obtained in atomistic computations, if their mean free paths and correlation scales are long. Our approach is to find efficient scale-separation strategies that combine analytical condensed-matter physics models describing long-range response and screening with ab-initio electronic structure computations of atomic-scale parameters, such as excitation spectra and electron-phonon and phonon-phonon couplings. Electronic and thermal transport in certain regimes can be predicted remarkably well using affordable computations, enabling quantitative understanding and design of electronic materials and random alloys for thermoelectric energy conversion. Figure below summarizes the discovery process we follow, starting from developing methods for computing electronic lifetimes to thermoelectric materials screening, synthesis and device characterization.


Interactions and transport in low-dimensional quantum devices

Recent progress in fabrication and characterization of 1D (nanotube) and 2D (atomically thin sheet) materials opened possibilities to create nano-scale devices operating on quantum level. Low dimensionality makes these materials highly tunable, and thus ideal for sensing and computing applications, but also highly fragile and difficult to study experimentally. We are interested in using first-principles-based quantum models to gain fundamental understanding of electronic interaction and transport characteristics of these materials, with particular attention to effects of external fields and substrates on device properties.