On truncations of the Chalker-Coddington model

Romain Couvreur (1, 2) , Eric Vernier , Jesper Lykke Jacobsen (1, 2, 3) , Hubert Saleur (2)

1 LPTENS - Laboratoire de Physique Théorique de l'ENS [École Normale Supérieure]
2 IPHT - Institut de Physique Théorique - UMR CNRS 3681
3 Champs Aléatoires et Systèmes hors d'Équilibre

The supersymmetric reformulation of physical observables in the Chalker-Coddington model (CC) for the plateau transition in the integer quantum Hall effect leads to a reformulation of its critical properties in terms of a 2D non-compact loop model or a 1D non-compact gl(2|2) spin chain. Following a proposal by Ikhlef, Fendley and Cardy [11] , we define and study a series of truncations of these loop models and spin chains, involving a finite and growing number of degrees of freedom per site. The case of the first truncation is solved analytically using the Bethe-ansatz. It is shown to exhibit many of the qualitative features expected for the untruncated theory, including a quadratic spectrum of exponents with a continuous component, and a normalizable ground state below that continuum. Quantitative properties are however at odds with the results of simulations on the CC model. Higher truncations are studied only numerically. While their properties are found to get closer to those of the CC model, it is not clear whether this is a genuine effect, or the result of strong finite-size corrections.

Mots clés: spin: chain; correction: finite size; Hall effect: quantum; supersymmetry; Bethe ansatz; numerical calculations

Domaines: Physique Générale [physics.gen-ph]; Physique mathématique [math-ph]

Romain Couvreur, Eric Vernier, Jesper Lykke Jacobsen, Hubert Saleur. On truncations of the Chalker-Coddington model. Nuclear Physics B, 2019, 941, pp.507-559. ⟨10.1016/j.nuclphysb.2019.02.015⟩. ⟨hal-01891249⟩