Condensed Matter Seminar: Connecting Landau (levels), Bardeen (polynomials) and Fermi (arcs)

Abstract:

Condensed matter systems realizing Weyl fermions exhibit striking phenomenology frequently rooted in the presence of topologically protected surface states (Fermi arcs) or the chiral anomaly driven by nonorthogonal external electric and magnetic fields. More recently, inhomogeneous strain or magnetization were predicted to result in chiral electric E5 and magnetic B5 fields, which modify and enrich the chiral anomaly with additional terms.  In this work we develop a lattice based, Landau and pseudo-Landau level picture of the chiral anomaly that treats all anomalous terms on equal footing and naturally incorporates Fermi arcs.

We exemplify its potential by i) physically interpreting the largely overlooked role of Fermi arcs in the covariant (Fermi level) contribution to the anomaly and ii) revisiting the factor of 1/3 difference between the covariant and consistent (complete band) contribution to the E5.B5 term in the anomaly.

We find that the latter is only obtained for profiles of B5 where the Weyl fermions are separated in both real and momentum space.

Our framework provides a versatile tool for the analysis of anomalies in realistic lattice models as well as a source of simple physical intuition for understanding strained and magnetized inhomogeneous Weyl semimetals.

Event Organizer: Prof. Alexander Gerber