Charge-4$e$ Superconductivity in a Hubbard model

Abstract

A phase of matter in which fermion quartets form a superconducting condensate, rather than the paradigmatic Cooper pairs, is a recurrent subject of experimental and theoretical studies. However, a comprehensive microscopic understanding of charge-4$e$ superconductivity as a quantum phase is lacking. Here, we propose and study a two-orbital tight-binding model with attractive Hubbard-type interactions. Such a model naturally provides the Bose-Einstein condensate as a limit for electron quartets and supports charge-4$e$ superconductivity, as we show by mapping it to a spin-1/2 chain in this perturbative limit. Using both exact diagonalization and density matrix renormalization group calculations for the one-dimensional case, we further establish that the ground state is indeed a superfluid phase of 4$e$ charge carriers and that this phase can be stabilized well beyond the perturbative regime. Importantly, we demonstrate that 4$e$ condensation dominates over 2$e$ condensation even for nearly decoupled orbitals, a scenario suitable for experiments with ultracold atoms in the form of almost decoupled chains. Our model paves the way for both experimental and theoretical exploration of 4$e$ superconductivity and provides a natural starting point for future studies beyond one dimension or more intricate 4$e$ states.

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• Cooper quartets in interacting hybrid superconducting systems
• Thermomodulated intrinsic Josephson effect in Kagome CsV3Sb5
• Vestigial $d$-wave charge-$4e$ Superconductivity from Bidirectional Pair Density Waves
• Fluctuation conductivity in ultraclean multicomponent superconductors
• Trion formation and ordering in the attractive SU(3) Fermi-Hubbard model
• Edge-Edge Correlations without Edge-States: $\eta$-clustering State as Ground State of the Extended Attractive SU(3) Hubbard Chain