Pronoy Sircar’s PhD Thesis Defense

Weyl semimetals are three dimensional topological states of matter whose band structures are characterized by the presence of points of degeneracy between bands near the Fermi energy. These points can appear in three-dimensional materials that break at least one of inversion or time reversal symmetry. Their presence in a band structure, and the consequent emergence of chiral species of particles that are mirror images of one another, leads to macroscopic behavior that is qualitatively different from normal metals, including Chiral Anomaly and the related phenomenon of Negative Magnetoresistance.

In this thesis, we develop a hydrodynamic description for a Weyl semimetal, suitable for modelling slow out of equilibrium situations such as are commonly encountered in typical transport experiments. Our analysis is based on macroscopic reasoning such as symmetry considerations and positivity of Entropy production.  Using this phenomenological model, we explain magnetoresistance, and the related effect of magnetic enhancement to the thermoelectric conductivity. We also touch upon some general aspects of formulation of hydrodynamic theories for solid state electronic systems.