Abstract: Superconductivity without Quasiparticles
Superconductivity is often found in the vicinity of quantum critical points, where strong fluctuations suppress the formation of Fermi-liquid quasiparticles and the conventional Bardeen–Cooper–Schrieffer (BCS) theory ceases to apply. In this talk, we discuss how an understanding of pairing can nevertheless be achieved in quantum-critical systems. We focus on two examples: an Ising ferromagnetic quantum critical point in a compressible electronic system and the Gross–Neveu transition in Dirac materials near charge neutrality. The latter may be particularly relevant to the superconductivity observed in twisted and moiré materials, where charge neutrality, strong correlations, and competing orders play a central role. We also establish a connection to holographic superconductivity, a framework rooted in the duality between quantum field theories and gravitational theories that has been proposed as a description of strongly interacting systems lacking quasiparticle excitations. Specifically, we derive holographic superconductivity in the form of a gravitational theory with an emergent space-time geometry directly from a quantum many-body Hamiltonian.
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