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O: Fachverband Oberflächenphysik
O 4: Topology and Symmetry-Protected Materials
O 4.2: Talk
Monday, September 5, 2022, 10:45–11:00, H6
Momentum space signatures of Berry flux monopoles in a Weyl semimetal — •Maximilian Ünzelmann1,3, Tim Figgemeier1,3, Philipp Eck2,3, Begmuhammet Geldiyev1,3, Domenico Di Sante2,3, Giorgio Sangiovanni2,3, Hendrik Bentmann1,3, and Friedrich Reinert1,3 — 1Experimentelle Physik 7, Universität Würzburg — 2Theoretische Physik 1, Universität Würzburg — 3Würzburg-Dresden Cluster of Excellence ct.qmat
An intriguing property of Weyl semimetals (WSM) is that they feature topologically protected crossings of the spin-polarized valence and conduction bands in their three-dimensional bulk band structure. These crossing points – the Weyl points (WP) – can be considered as ’magnetic’ monopoles, which, however, are not located in real space but rather in momentum space. The topological (monopole) character manifests itself in the momentum-dependence of the electronic wave functions, which is investigated in the paradigmatic WSM TaAs, using bulk-sensitive soft X-ray angle-resolved photoelectron spectroscopy combined with spin-resolved measurements and circular dichroism (CD) [1]. The latter addresses the local orbital angular momentum (OAM), which exhibits a non-trivial winding around the WP, similar to the Berry curvature, i.e., the k-space magnetic field. The momentum-dependent modulation of the OAM around the WP – observed in density functional theory calculations and CD-ARPES – thus denotes a direct signature for the Berry flux monopoles in TaAs.
[1] M. Ünzelmann et al., Nat. Commun., 12, 3650 (2021)