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TT: Fachverband Tiefe Temperaturen

TT 43: Focus Session: Topology in 3D Reciprocal Space: Beyond Dirac and Weyl Quasiparticles (joint session TT/MA)

TT 43.4: Hauptvortrag

Mittwoch, 3. April 2019, 16:45–17:15, H2

Evidence for an axionic charge density wave in the Weyl semimetal (TaSe₄)₂I — •Johannes Gooth — Max Planck Institut für Chemische Physik fester Stoffe

An axion insulator is a correlated topological phase, predicted to arise from the formation of a charge density wave in Weyl semimetals. The accompanying sliding mode in the charge density wave phase, the phason, is an axion. It is expected to cause anomalous magneto-electric transport effects. However, this axionic charge density wave has so far eluded experimental detection. In this paper, we report for the first time the observation of a large, positive contribution to the magneto-conductance in the sliding mode of the charge density wave Weyl semimetal (TaSe₄)₂I for collinear electric and magnetic fields (E||B). The positive contribution to the magneto-conductance originates from the anomalous axionic contribution of the chiral anomaly to the phason current, and is locked to the parallel alignment of E and B. By rotating B, we show that the angular dependence of the magneto-conductance is consistent with the anomalous transport of an axionic charge density wave.