Seminario di Fisica Teorica
Higher-dimensional topological phases play a key role in understanding the lower-dimensional topological phases and the related topological responses through a dimensional reduction procedure. In this talk, I present a 4+1-D Dirac-type Hamiltonian protected by CP-symmetry, whose 3D boundary supports an odd number of Dirac cones. This system supports (4+1)-D quantum spin and valley Hall effects. A specific perturbation splits each bulk massive Dirac cone into two valleys separated in energy-momentum space with opposite second Chern numbers, in which the 3D boundary modes become a nodal sphere or a Weyl semi-metallic phase. By introducing the electromagnetic (EM) and pseudo-EM fields, exotic topological responses of our system are revealed, which are found to be described by the (4+1)-D mixed Chern-Simons theories in the low-energy regime. Notably, several topological phase transitions occur when the bulk gap closes by giving rise to exotic double-nodal-line/nodal-hyper-torus gapless phases. Finally, I show how to probe experimentally these topological effects in cold atoms.
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Topic: Theory and Pheno seminars
Meeting ID: 857 318 5271