Exotic transport phenomena in quantum materials from ab initio

Exotic transport phenomena provide a powerful way to probe excited states in quantum materials. Emergent signatures can arise when the length scales of momentum-relaxation/conservation for the nearly-free electron are comparable. There, the carriers flow collectively and the conventional diffusive transport description from textbook is not sufficient to fully capture the charge conduction in the hydrodynamic regime [1]. 

We use ab initio methods to investigate this exotic transport phenomenon. First, we focus on the electron-phonon interactions and show how they give rise to anomalous behaviors from both electron and phonon specifics in two prototypical semimetals WP₂ and WTe₂ [2-4]. We show that rapid e-ph scattering can lead to indirect electron-electron interactions, which conserves the total electron momentum. By solving the numerical BTE with the ab initio input, we demonstrate that the current density distribution in a thin long channel resembles a parabolic flow pattern [2,5]. Inspired by the recent space-resolved measurements, we characterize the different transport regimes in the parameter space of lmr, lmc, and w. Finally, we present predictions on candidates ZrSiS and TaAs₂ and propose design principles to realize hydrodynamics in anisotropic metals and semimetals [6].