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Main Authors: Xu, Qiao-Ru, Wu, Congjun
Format: Preprint
Published: 2026
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Online Access:https://arxiv.org/abs/2605.29338
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author Xu, Qiao-Ru
Wu, Congjun
author_facet Xu, Qiao-Ru
Wu, Congjun
contents We develop a theory of superconductivity (or superfluidity) based on condensed fermion quartets focusing on the dilute spin-$\frac{1}{2}$ systems at zero temperature. In the spirit of the Bardeen--Cooper--Schrieffer ansatz, a variational wavefunction is constructed such that, within the so-called ``dilute quartet approximation", it is the ground state of an effective quartic Hamiltonian. For a given two-body interaction in favor of quartetting, the gap parameter is suitably defined and the gap equation is also derived. As to the excited states, an intuitive physical picture based on a sixteen-dimensional ``occupation space" is depicted and the associated eigen-energies are obtained. This theory is applied to compute the superfluid fraction, which is found to be the same as in conventional superconductors, despite the interacting nature of the quartet problem.
format Preprint
id arxiv_https___arxiv_org_abs_2605_29338
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Effective Theory of Fermion Quartet Condensation
Xu, Qiao-Ru
Wu, Congjun
Superconductivity
Quantum Gases
We develop a theory of superconductivity (or superfluidity) based on condensed fermion quartets focusing on the dilute spin-$\frac{1}{2}$ systems at zero temperature. In the spirit of the Bardeen--Cooper--Schrieffer ansatz, a variational wavefunction is constructed such that, within the so-called ``dilute quartet approximation", it is the ground state of an effective quartic Hamiltonian. For a given two-body interaction in favor of quartetting, the gap parameter is suitably defined and the gap equation is also derived. As to the excited states, an intuitive physical picture based on a sixteen-dimensional ``occupation space" is depicted and the associated eigen-energies are obtained. This theory is applied to compute the superfluid fraction, which is found to be the same as in conventional superconductors, despite the interacting nature of the quartet problem.
title Effective Theory of Fermion Quartet Condensation
topic Superconductivity
Quantum Gases
url https://arxiv.org/abs/2605.29338