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X-WR-CALDESC:Events for Dirac Materials
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DTSTART:20190331T010000
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DTSTART:20191027T010000
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DTSTART;TZID="Europe/Stockholm":20191008T161500
DTEND;TZID="Europe/Stockholm":20191008T170000
DTSTAMP:20260613T055802
CREATED:20190925T180612Z
LAST-MODIFIED:20191007T115925Z
UID:1368-1570551300-1570554000@diracmaterials.org
SUMMARY:[Group Meeting] Adrien Bouhon - Weyl Nodes with Non-Abelian Charges
DESCRIPTION:Abstract:\nWeyl points trapped within a C_2T-symmetric plane (C2 = 180 degrees rotation\, and T = time reversal) possess non-Abelian topological charges on top of their chirality. E.g. three-level systems realize the quaternion group. This picture requires to go beyond the modeling of a band structure as a Grassmannian (where a single spectral gap is specified). The non-Abelian nature of Weyl points implies new types of obstruction\, where\, for instance\, two Weyl points with opposite chiralities may not annihilate. Also\, the non-Abelian charges can be converted through the braiding of Weyl points in momentum space. \n \nI will review three different yet equivalent ways of computing the non-Abelian charges: (i) as a non-cyclic phase defined from the parallel transport of the Hamiltonian along a base loop\, (ii) as the Euler class of a two-band subspace over a patch bounded by the base loop\, and (iii) as the winding number of the Pfaffian of the Wilsonnian Hamiltonian – of the two-band subspace – as the base loop flows over the patch.  \n \n
URL:http://diracmaterials.org/calendar2/group-meeting-adrien-bouhon-weyl-nodes-with-non-abelian-charges/
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