Special Emergent Phenomena Seminar 290S/QM Seminar Speaker Jonah Herzog-Arbeitman (Princeton) Monday, May 16 at 3:00 pm

Time/Venue Monday, May 16 27 at 3:00 pm, 325 Physics South and Zoom: https://berkeley.zoom.us/j/99523499113pwd=REovb3pyam03WXQwbEhrU3dqNHZvdz09 , Meeting ID: 995 2349 9113 Passcode: 600704
Host Mike Zaletel
Title Exact Results for the Cooper Pair Spectrum of Flat Band Hubbard Models
Abstract In a flat band superconductor, bosonic excitations disperse while the unpaired electrons are completely immobile. To study this strongly interacting system, Tovmasyan et al. identified a class of Hubbard models possessing an eta-pairing symmetry and analytical ground states when a requirement called the uniform pairing condition is satisfied. In fact, we show that perfectly flat bands with uniform pairing can be guaranteed systematically from the orbitals alone in all space groups, thereby showing this family of Hamiltonians is very large. We study their many-body excitations and find that the Cooper pair (and Goldstone) bound states obey an effective single-particle Hamiltonian. It possesses a unique gapless band, akin to the Feynman mode, whose quadratic dispersion is determined by the minimal quantum metric, thereby connecting the bulk topology of the flat bands to the many-body spectrum. Perturbing away from the flat band limit, we show that the strongest superconductivity occurs at half filling, not at the highest density of states. This is similar to the superconductivity observed in twisted bilayer graphene.

This entry was posted in QM Seminar. Bookmark the permalink.