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arXiv:2307.11937 · Physical review. B./Physical review. B

Fermion quartets on the square lattice

D. Baeriswyl, Francesco Petocchi, Philipp Werner

Published Sep 15, 2023• 0 citations
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Abstract

We study a microscopic model for four spinless fermions on the square lattice which exhibits a quartet bound state in the strong coupling regime. The four-particle quantum states are analyzed using symmetry arguments and by introducing a zoo of relevant lattice animals. These considerations, as well as variational and exact diagonalization calculations, demonstrate the existence of a narrow quartet band at small hopping and a first-order transition to delocalized fermions at a critical hopping parameter, in qualitative contrast to, e.g., the BCS-BEC crossover in the attractive Hubbard model. In the case of pure attraction, an intermediate phase is found, in which a more extended and presumably more mobile hybrid quartet dominates the ground state. We comment on the relevance of the spin degree of freedom and on the reasons why electron quartetting is rarely observed in real materials.

DOI
10.1103/physrevb.108.115133

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Quantum phases of two-dimensional Z2\mathbb{Z}_2Z2​ gauge theory coupled to spinless fermion matter
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