Engineering holographic flat fermionic bands
Abstract
In electronic systems with flat bands, such as twisted bilayer graphene, interaction effects govern the structure of the phase diagram. In this paper, we show that a strongly interacting system featuring fermionic flat bands can be engineered using the holographic duality. In particular, we find that in the holographic nematic phase, two bulk Dirac cones separated in momentum space at low temperature, approach each other as the temperature increases. They eventually collide at a critical temperature yielding a flattened band with a quadratic dispersion. On the other hand, in the symmetric (Lifshitz) phase, this quadratic dispersion relation holds for any finite temperature. We therefore obtain a first holographic, strongcoupling realization of a topological phase transition where two Berry monopoles of charge one merge into a single one with charge two, which may be relevant for two and threedimensional topological semimetals.
 Publication:

Physical Review D
 Pub Date:
 April 2022
 DOI:
 10.1103/PhysRevD.105.L081902
 arXiv:
 arXiv:2112.12198
 Bibcode:
 2022PhRvD.105h1902G
 Keywords:

 High Energy Physics  Theory;
 Condensed Matter  Strongly Correlated Electrons
 EPrint:
 6 pages, 3 figures