High-temperature charge-4e superconductivity in SU(4) interacting fermions

TL;DR

This paper introduces a sign-problem-free model demonstrating high-temperature charge-4e superconductivity in two dimensions, with robust phase transitions and potential experimental realizations.

Contribution

It provides the first concrete microscopic model showing robust charge-4e superconductivity at high temperatures using unbiased quantum Monte Carlo simulations.

Findings

Charge-4e SC is the primary ground state in the strong-coupling regime.

Charge-4e SC exhibits a Berezinskii-Kosterlitz-Thouless transition with a universal stiffness jump.

Transition temperature Tc increases nearly linearly with interaction strength.

Abstract

The condensation of electron quartets, known as charge-4e superconductivity (SC), represents a novel quantum state of matter beyond the standard paradigm of Cooper pairing. However, concrete microscopic models realizing this phase in two dimensions remain a central challenge. Here, we introduce a non-engineered and sign-problem-free model, unambiguously demonstrating the emergence of a robust and high-temperature charge-4e SC phase using unbiased quantum Monte Carlo simulations. At zero temperature, the phase diagram reveals that charge-4e SC is the primary ground state in the strong-coupling regime. At finite temperature in the absence of charge-2e SC, we identify charge-4e SC through a Berezinskii-Kosterlitz-Thouless transition, marked by a universal jump in the superfluid stiffness consistent with a condensate of charge 4e. Remarkably, the transition temperature Tc increases nearly linearly with interaction strength, providing a robust mechanism for high-Tc quartet superconductivity. Furthermore, spectral analysis reveals a prominent pseudogap above Tc arising from strong phase fluctuations. Our results establish a canonical and numerically exact model system for charge-4e superconductivity, offering crucial guidance for its realization in experimental platforms such as moir\'e materials and ultracold atomic systems.