Department Colloquium: Tuesday, February 7, 2023 - Topological protection of Weyl fermions visualized on the atomic scale - protection, fragility and cooperation

Event Date: 

Tuesday, February 7, 2023 - 3:45pm

Event Date Details: 

This event will be in-person and on Zoom.

Event Location: 

  • Broida 1640 and Zoom
  • Physics Department Colloquium

This event will be in-person and on Zoom.

Haim Beidenkopf, Weizmann Institute of Science

Topological protection of Weyl fermions visualized on the atomic scale - protection, fragility and cooperation

 

Topological electronic materials host exotic boundary modes, that cannot be realized as standalone states, but only at the boundaries of a topologically classified bulk. Topological semimetals, whose bulk electrons exhibit chiral Dirac-like dispersion, host Fermi-arc states on their boundaries. These surface bands disperse along open momentum contours terminating at the surface projections of the bulk Dirac nodes with opposite chirality. Such reduction of the surface degrees of freedom by their segregation to opposite surfaces of the sample is common to all topological states of matter and provides topological protection from their surface elimination. I will discuss three topological semimetallic systems that show distinct, though consistent, level of robustness. In the inversion symmetry broken Weyl semimetal TaAs the Fermi arc surface states hardly adhere to the underlying lattice potential. In contrast, in the time reversible symmetry broken Weyl semimetal Co3Sn2S2 the dispersion of the topological Fermi-arc bands, and even their inter-Weyl node connectivity, are found to vary with the surface potential. Our recent study of the ferromagnetic nodal line semimetal Fe3GeTe2 reveals that Weyl fermions may in fact cooperate with disorder and interactions to induce an anomalous Hall insulating state of superior protection akin to the role of disorder in stabilizing the integer quantum Hall effect. We thus show a diverse response of topological semimetals to perturbations that may accordingly offer diverse ability to control and manipulate them.

 

 

 

 

ZOOM INFO: https://ucsb.zoom.us/j/84217234934?pwd=Nk4ya1NLaWVMUVJLMEllcHJzQmRkdz09