Dresden 2026 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 13: Focus Session: New Routes to Localization and Quantum Non-Ergodicity II (joint session TT/DY)
DY 13.1: Talk
Monday, March 9, 2026, 15:00–15:15, CHE/0091
Localized obstructed pairs with zero superfluid stiffness from doping an antiferromagnetic insulator — •Tamaghna Hazra1, Nishchhal Verma2, and Jörg Schmalian1 — 1Institüt für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie, Karlsruhe, Germany — 2Department of Physics, Columbia University
Doping a Mott antiferromagnet is widely expected to yield mobile Cooper pairs whose kinetic energy sets the superfluid stiffness. We show instead that, when doped charges propagate on the line graph of a lattice with strong antiferromagnetic exchange, they bind into obstructed Cooper pairs, which are compact localized bosons that possess zero superfluid stiffness at leading order in the strong-coupling expansion. The pair-hopping Hamiltonian generates an exactly flat bosonic band whose compact localized states dominate the low-energy Hilbert space, yielding a ground-state manifold with extensive degeneracy and a phase stiffness that vanishes anomalously as the third inverse power of the pairing strength in the strong-coupling limit. At quarter filling, the frustrated dynamics maps onto a quantum dimer model at the Rokhsar-Kivelson point, realizing a d-wave resonating-valence-bond spin liquid with topological ground-state degeneracy and deconfined holon excitations. Our results establish a mechanism for interaction-driven localization without disorder, in which strong magnetically-mediated pairing produces Cooper pairs whose kinetic energy collapses to zero, revealing a distinct failure mode of unconventional superconductivity in strongly-correlated materials.
Keywords: superconductivity; superfluid stiffness; frustrated magnetism; dimer model; flat band superconductivity