A solvable non-unitary fermionic long-range model with extended symmetry

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Hauptverfasser: Moussa, Adel Ben, Lamers, Jules, Serban, Didina, Toufik, Ayman
Format: Preprint
Veröffentlicht: 2024
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author Moussa, Adel Ben
Lamers, Jules
Serban, Didina
Toufik, Ayman
author_facet Moussa, Adel Ben
Lamers, Jules
Serban, Didina
Toufik, Ayman
contents We define and study a long-range version of the XX model, arising as the free-fermion point of the XXZ-type Haldane--Shastry (HS) chain. It has a description via non-unitary fermions, based on the free-fermion Temperley--Lieb algebra, and may also be viewed as an alternating $\mathfrak{gl}(1|1)$ spin chain. Even and odd length behave very differently; we focus on odd length. The model is integrable, and we explicitly identify two commuting hamiltonians. While non-unitary, their spectrum is real by PT-symmetry. One hamiltonian is chiral and quadratic in fermions, while the other is parity-invariant and quartic. Their one-particle spectra have two linear branches, realising a massless relativistic dispersion on the lattice. The appropriate fermionic modes arise from 'quasi-translation' symmetry, which replaces ordinary translation symmetry. The model exhibits exclusion statistics, like the isotropic HS chain, with even more 'extended symmetry' and larger degeneracies.
format Preprint
id arxiv_https___arxiv_org_abs_2404_10164
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle A solvable non-unitary fermionic long-range model with extended symmetry
Moussa, Adel Ben
Lamers, Jules
Serban, Didina
Toufik, Ayman
Strongly Correlated Electrons
High Energy Physics - Theory
Mathematical Physics
Exactly Solvable and Integrable Systems
We define and study a long-range version of the XX model, arising as the free-fermion point of the XXZ-type Haldane--Shastry (HS) chain. It has a description via non-unitary fermions, based on the free-fermion Temperley--Lieb algebra, and may also be viewed as an alternating $\mathfrak{gl}(1|1)$ spin chain. Even and odd length behave very differently; we focus on odd length. The model is integrable, and we explicitly identify two commuting hamiltonians. While non-unitary, their spectrum is real by PT-symmetry. One hamiltonian is chiral and quadratic in fermions, while the other is parity-invariant and quartic. Their one-particle spectra have two linear branches, realising a massless relativistic dispersion on the lattice. The appropriate fermionic modes arise from 'quasi-translation' symmetry, which replaces ordinary translation symmetry. The model exhibits exclusion statistics, like the isotropic HS chain, with even more 'extended symmetry' and larger degeneracies.
title A solvable non-unitary fermionic long-range model with extended symmetry
topic Strongly Correlated Electrons
High Energy Physics - Theory
Mathematical Physics
Exactly Solvable and Integrable Systems
url https://arxiv.org/abs/2404.10164