Primary charge-4e superconductivity from doping a featureless Mott insulator

TL;DR

This paper proposes that doping a featureless Mott insulator with $SU(4)$ symmetry can naturally lead to primary charge-$4e$ superconductivity, supported by theoretical analysis and DMRG simulations of a bilayer Hubbard model.

Contribution

It introduces a new microscopic model and theoretical framework demonstrating primary charge-$4e$ superconductivity at zero temperature in a doped Mott insulator.

Findings

Identification of a charge-$4e$ superconducting phase in the $SU(4)$ ESD model.

Observation of a conventional charge-$2e$ superconducting phase in the $Sp(4)$ case.

Characterization of the normal states and finite temperature phase diagram.

Abstract

Superconductivity is usually understood as a phase in which charge-$2e$ Cooper pairs are condensed. Charge-$4e$ superconductivity has largely been discussed as a vestigial order at finite temperature emerging from charge-$2e$ states. Primary charge-$4e$ superconducting phases at zero temperature remain scarce in both experiments and microscopic models. Here we argue that a doped featureless Mott insulator with $SU(4)$ symmetry provides a natural platform for primary charge-$4e$ superconductivity, based on perturbative renormalization group arguments and group theoretic considerations. As a concrete realization, we construct a bilayer Hubbard model with tunable onsite $SU(4)$ and $Sp(4)$ symmetries that exhibits a featureless Mott insulating phase at half filling. Its low energy physics is captured by a generalized ESD model, featuring an effective Hamiltonian that is purely kinetic within the constrained Hilbert space. Using density matrix renormalization group (DMRG) simulations, we find a primary charge-$4e$ superconducting phase in the $SU(4)$ ESD model and a conventional primary charge-$2e$ phase in the $Sp(4)$ case. We further characterize the corresponding normal states and discuss the resulting finite temperature phase diagram.