Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:cond-mat/0612270 · Journal of Statistical Mechanics Theory and Experiment

Cooper pairs and exclusion statistics from coupled free-fermion chains

Paul Fendley, Kareljan Schoutens

Published Feb 22, 2007• 24 citations
arXivHTMLPDF

Abstract

We show how to couple two free-fermion chains so that the excitations consist of Cooper pairs with zero energy, and free particles obeying (mutual) exclusion statistics. This behaviour is reminiscent of anyonic superconductivity, and of a ferromagnetic version of the Haldane–Shastry spin chain, although here the interactions are local. We solve this model using the nested Bethe ansatz, and find all the eigenstates; the Cooper pairs correspond to exact-string or '0/0' solutions of the Bethe equations. We show how the model possesses an infinite-dimensional symmetry algebra, which is a supersymmetric version of the Yangian symmetry algebra for the Haldane–Shastry model.

DOI
10.1088/1742-5468/2007/02/p02017

Related papers

Haldane Fractional Statistics for 1D Heisenberg Spin XXX Chain

Wei-Jia Liu, Jiajia Luo, Xi-Wen Guan

Haldane's fractional exclusion statistics (FES) describes a generalized Pauli exclusion statistics, which can be regarded as an emergent quantum statistics induced by the intrinsic dynamical interaction. A non-mutual FES has been identified at the quantum criticality of the one-dimensional (1D) and 2D interacting Bose Gas [Nat. Sci. Rev. 9, nwac027 (2022)]. It is naturally asked if such a non-mutual FES can be induced by the spin-spin interaction in the antiferromagnetic spin-1/2 XXX chain? In this article, we first represent the Bethe ansatz equations of spin strings in terms of the FES equations of different species. Then we show that the 1D spin XXX chain remarkably possesses the non-mutual FES in the critical region. We observe that the equation of state in terms of the FES gives rises to full statistical properties of the model at quantum criticality, which are in good agreement with the results obtained from the thermodynamic Bethe ansatz (TBA) equations of the model. From the non-mutual FES, we also precisely determine the quantum scaling functions, which further agree well with the previous TBA results [Phys. Rev. B 96, 220401(R) (2017)]. Finally, we also build up an exact mapping between the scaling functions of the Lieb-Liniger model and the spin Heisenberg spin chain at quantum criticality. Our method provides deep insights into the critical phase of matter from quantum FES point of view.

arXiv:2503.01356•Mar 3, 2025•0 citations

Exact solution of a one-dimensional fermion model with interchain tunneling

R. Z. Bariev, Andreas Klümper, Andreas Schadschneider +1 more

A fermion model consisting of two chains with interchain tunneling is formulated and solved exactly by the Bethe-ansatz method. The interchain tunneling leads to Cooper-pair-like bound states and a threshold energy is required to overcome the binding energy. The correlation functions manifest superconducting properties.

arXiv:cond-mat/9409084•Physical review. B, Condensed matter•Oct 1, 1994•18 citations

Quasiparticles in quantum spin chains with strong axial exchange anisotropy

Lu, Ping

The quasiparticle composition of the eigenstates of quantum spin chains with nearest-neighbor exchange coupling subject to strong axial anisotropy is the focus of this dissertation. Complementary sets of quasiparticles are generated from opposite ends of the spectrum for the systematic generation of all eigenstates. The exclusion statistics of all quasiparticles thus introduced are determined exactly and used, in selected cases, for the exact thermodynamic analysis of the underlying spin chain model. This project starts from the Ising model with spin s = 1/2 and then branches out to the spin s = 1/2 XXZ model in the axial regime and to the spin s = 1 Ising model. In the s = 1/2 Ising case, the two complementary sets of quasiparticles are antiferromagnetic domain walls (solitons) and ferromagnetic domains (strings). In the s = 1 Ising case, they are soliton pairs and nested strings, respectively. The string quasiparticles of the s = 1/2 Ising chains are identified as limiting cases of Bethe ansatz solutions of the axial XXZ model. The thermodynamics of the Ising chain for s 1/2 is shown to be equivalent to that of a system of two species of solitons and for s = 1 to that of a system of six species of soliton pairs. Solitons exist on single bonds but soliton pairs may be spread across many bonds. The thermodynamics of a system of domains spanning up to M lattice sites is amenable to exact analysis and shown to become equivalent, in the limit M → ∞, to the thermodynamics of the s = 1/2 Ising chain. A relation is presented between the solitons in the Ising limit and the spinons in the XX limit of the s = 1/2 XXZ chain. The exclusion statistics is semionic for both spinons and solitons but the spinon vacuum is unique whereas the soliton vacuum is twofold with broken symmetry.

•Jan 1, 2009•0 citations

One-Dimensional Interacting Anyon Gas: Low-Energy Properties and Haldane Exclusion Statistics

Murray T. Batchelor, Xin Guan, N. Oelkers

The low-energy properties of the one-dimensional anyon gas with a delta-function interaction are discussed in the context of its Bethe ansatz solution. It is found that the anyonic statistical parameter and the dynamical coupling constant induce Haldane exclusion statistics interpolating between bosons and fermions. Moreover, the anyonic parameter may trigger statistics beyond Fermi statistics for which the exclusion parameter alpha is greater than one. The Tonks-Girardeau and the weak coupling limits are discussed in detail. The results support the universal role of alpha in the dispersion relations.

arXiv:cond-mat/0603643•Physical Review Letters•Jun 1, 2006•146 citations

Exact solvable model of coupled supersymmetric t-J chains

Igor N. Karnaukhov

An exact solvable model of the coupled supersymmetric t - J chains interacting via the spin exchange interaction is proposed and solved by the means of the nested Bethe ansatz. It is shown, that in addition to the direct spin-exchange interaction an effective interaction between fermions of different chains called as "an effective attractive hard-core interaction" is realized in the model. The critical exponents describing asymptotic behavior of the correlation functions are calculated using the Bethe ansatz equations and the finite-state scaling analysis in conformal field theory. It is shown that the two-component Tomonaga-Luttinger liquid with the dominating correlations of fermion pairs is realized in the low-density region. This non-traditional behavior of the correlation functions is realized due to the effective attractive hard-core interaction between particles.

Europhysics Letters (EPL)•Sep 26, 2008•0 citations

BCS model with asymmetric pair scattering: a non-Hermitian, exactly solvable Hamiltonian exhibiting generalized exclusion statistics

Jon Links, Amir Moghaddam, Yao-Zhong Zhang

We demonstrate the occurrence of free quasi-particle excitations obeying generalized exclusion statistics in a BCS model with asymmetric pair scattering. The results are derived from an exact solution of the Hamiltonian, which was obtained via the algebraic Bethe ansatz utilizing the representation theory of an underlying Yangian algebra. The free quasi-particle excitations are associated with highest weight states of the Yangian algebra, corresponding to a class of analytic solutions of the Bethe ansatz equations.

arXiv:1304.5818•Journal of Physics A Mathematical and Theoretical•Jul 5, 2013•1 citation
We show how to couple two free-fermion chains so that the excitations consist of Cooper pairs with zero energy, and free particles obeying (mutual) exclusion statistics. This behaviour is reminiscent of anyonic superconductivity, and of a ferromagnetic version of the Haldane–Shastry spin chain, although here the interactions are local. We solve this model using the nested Bethe ansatz, and find all the eigenstates; the Cooper pairs correspond to exact-string or '0/0' solutions of the Bethe equations. We show how the model possesses an infinite-dimensional symmetry algebra, which is a supersymmetric version of the Yangian symmetry algebra for the Haldane–Shastry model.
Haldane's fractional exclusion statistics (FES) describes a generalized Pauli exclusion statistics, which can be regarded as an emergent quantum statistics induced by the intrinsic dynamical interaction. A non-mutual FES has been identified at the quantum criticality of the one-dimensional (1D) and 2D interacting Bose Gas [Nat. Sci. Rev. 9, nwac027 (2022)]. It is naturally asked if such a non-mutual FES can be induced by the spin-spin interaction in the antiferromagnetic spin-1/2 XXX chain? In this article, we first represent the Bethe ansatz equations of spin strings in terms of the FES equations of different species. Then we show that the 1D spin XXX chain remarkably possesses the non-mutual FES in the critical region. We observe that the equation of state in terms of the FES gives rises to full statistical properties of the model at quantum criticality, which are in good agreement with the results obtained from the thermodynamic Bethe ansatz (TBA) equations of the model. From the non-mutual FES, we also precisely determine the quantum scaling functions, which further agree well with the previous TBA results [Phys. Rev. B 96, 220401(R) (2017)]. Finally, we also build up an exact mapping between the scaling functions of the Lieb-Liniger model and the spin Heisenberg spin chain at quantum criticality. Our method provides deep insights into the critical phase of matter from quantum FES point of view.
The quasiparticle composition of the eigenstates of quantum spin chains with nearest-neighbor exchange coupling subject to strong axial anisotropy is the focus of this dissertation. Complementary sets of quasiparticles are generated from opposite ends of the spectrum for the systematic generation of all eigenstates. The exclusion statistics of all quasiparticles thus introduced are determined exactly and used, in selected cases, for the exact thermodynamic analysis of the underlying spin chain model. This project starts from the Ising model with spin s = 1/2 and then branches out to the spin s = 1/2 XXZ model in the axial regime and to the spin s = 1 Ising model. In the s = 1/2 Ising case, the two complementary sets of quasiparticles are antiferromagnetic domain walls (solitons) and ferromagnetic domains (strings). In the s = 1 Ising case, they are soliton pairs and nested strings, respectively. The string quasiparticles of the s = 1/2 Ising chains are identified as limiting cases of Bethe ansatz solutions of the axial XXZ model. The thermodynamics of the Ising chain for s 1/2 is shown to be equivalent to that of a system of two species of solitons and for s = 1 to that of a system of six species of soliton pairs. Solitons exist on single bonds but soliton pairs may be spread across many bonds. The thermodynamics of a system of domains spanning up to M lattice sites is amenable to exact analysis and shown to become equivalent, in the limit M → ∞, to the thermodynamics of the s = 1/2 Ising chain. A relation is presented between the solitons in the Ising limit and the spinons in the XX limit of the s = 1/2 XXZ chain. The exclusion statistics is semionic for both spinons and solitons but the spinon vacuum is unique whereas the soliton vacuum is twofold with broken symmetry.
The low-energy properties of the one-dimensional anyon gas with a delta-function interaction are discussed in the context of its Bethe ansatz solution. It is found that the anyonic statistical parameter and the dynamical coupling constant induce Haldane exclusion statistics interpolating between bosons and fermions. Moreover, the anyonic parameter may trigger statistics beyond Fermi statistics for which the exclusion parameter alpha is greater than one. The Tonks-Girardeau and the weak coupling limits are discussed in detail. The results support the universal role of alpha in the dispersion relations.
An exact solvable model of the coupled supersymmetric t - J chains interacting via the spin exchange interaction is proposed and solved by the means of the nested Bethe ansatz. It is shown, that in addition to the direct spin-exchange interaction an effective interaction between fermions of different chains called as "an effective attractive hard-core interaction" is realized in the model. The critical exponents describing asymptotic behavior of the correlation functions are calculated using the Bethe ansatz equations and the finite-state scaling analysis in conformal field theory. It is shown that the two-component Tomonaga-Luttinger liquid with the dominating correlations of fermion pairs is realized in the low-density region. This non-traditional behavior of the correlation functions is realized due to the effective attractive hard-core interaction between particles.
We demonstrate the occurrence of free quasi-particle excitations obeying generalized exclusion statistics in a BCS model with asymmetric pair scattering. The results are derived from an exact solution of the Hamiltonian, which was obtained via the algebraic Bethe ansatz utilizing the representation theory of an underlying Yangian algebra. The free quasi-particle excitations are associated with highest weight states of the Yangian algebra, corresponding to a class of analytic solutions of the Bethe ansatz equations.