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 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 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 charge carriers and that this phase can be stabilized well beyond the perturbative regime. Importantly, we demonstrate that 4 condensation dominates over 2 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 superconductivity and provides a natural starting point for future studies beyond one dimension or more intricate 4 states.
Cite
@article{arxiv.2312.13348,
title = {Charge-4$e$ Superconductivity in a Hubbard model},
author = {Martina O. Soldini and Mark H. Fischer and Titus Neupert},
journal= {arXiv preprint arXiv:2312.13348},
year = {2024}
}