Orbital-active honeycomb materials

author: time:2019-07-03 clicks:

Time and place: 2019.7.4, 14:30 pm, Wuhan National High Magnetic Field Center B206

Presenter: Congjun Wu

TitleOrbital-active honeycomb materials

Abstract:

We provide a unified view for a class of orbital-active honeycomb materials, including bis-muthene, stanene, exciton-polarition lattice, and the recent focus of the twisted bilayer graphene. These materials are orbital-active possessing a pair of degenerate px and py orbitals on each site, which are unified under the E-representation of the C6v group symmetry. We started the research on orbital-active honeycomb systems in ultra-cold atom optical lattices, and found that similar physics also applies to the above solid state materials unified under the same symmetry structure. For solid state applications, we propose a new mechanism to boost the topological gap to the full scale of the atomic spin-orbit coupling, i.e., the order of 1eV. This mechanism has been recently realized in experiments of bismuthene on SiC, which shows the evidence of the gap up to 0.67eV. Mech-anism for unconventional superconductivity assisted by the orbital structure in this class of mate-rials is also studied. The flat band structure arises in 2D orbital-active honeycomb materials, such as organic metal frameworks and transition metal oxide films, in which strong correlation phe-nomena including Wigner crystallization and ferromagnetism appear.

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