SKM 2023 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 53: Graphene

TT 53.8: Vortrag

Donnerstag, 30. März 2023, 17:00–17:15, HSZ 204

Theory of broken symmetry quantum Hall states in the N=1 Landau level of Graphene — •Nikolaos Stefanidis¹ and Inti Sodemann^2,1 — ¹Max-Planck-Institut für Physik komplexer Systeme, Dresden 01187, Germany — ²Institut für Theoretische Physik, Universität Leipzig, D-04103, Leipzig, Germany

We study many-body ground states for the partial integer fillings of the N=1 Landau level in graphene, by constructing a model that accounts for the lattice scale corrections to the Coulomb interactions. Interestingly, in contrast to the N=0 Landau level, this model contains not only pure delta function interactions but also some of its derivatives. Due to this we find several important differences with respect to the N=0 Landau level. For example at quarter filling when only a single component is filled, there is a degeneracy lifting of the quantum hall ferromagnets and ground states with entangled spin and valley degrees of freedom can become favourable. Moreover at half-filling of the N=1 Landau level, we have found a new phase that is absent in the N=0 Landau level, that combines characteristics of the Kekulé state and an antiferromagnet. We also find that according to the parameters extracted in a recent experiment, at half-filling of the N=1 Landau level graphene is expected to be in a delicate competition between an AF and a CDW state, but we also discuss why the models for these recent experiments might be missing some important terms.