Topological semimetals are three-dimensional crystalline materials where electronic energy bands disperse linearly from bulk nodes. While gapless, they nevertheless have robust topological properties akin to their insulating cousins. Studying these via transport measurements is challenging, owing to the inevitable complication that 'normal' bulk conduction masks the more subtle topological phenomena. I will present theoretical arguments that show how non-local transport measurements in a magnetic field may be used to circumvent this problem in two ways. First, the bulk chiral anomaly may be detected via a nonlocal resistance in a Hall geometry. Second, the surface "Fermi arcs" give rise to resonant transmission of microwave radiation across a slab, with a resonant frequency that is dependent both on perpendicular field and sample size. Importantly, both these experiments rely only on a long charge relaxation time, rather than a long phase coherence time, and are therefore relatively robust against disorder. I will comment on the applicability of these ideas to both Weyl and Dirac semimetals.
References:
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