Higher-dimensional Quantum Spin and Valley Hall Effects in Synthetic Matter

Friday, November 18, 2022 - 14:00 to 15:00
Hall A, North Campus, Maynooth University

Join guest Seminar Speaker Giandomenico Palumbo, Dublin Institute for Advanced Studies (DIAS) when he discusses Higher-dimensional Quantum Spin and Valley Hall Effects in Synthetic Matter

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.

For those who wish to attend online, we have set up a Microsoft Teams meeting.

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