Spin susceptibility of underdoped cuprates: the case of Ortho-II YBa_2Cu_3O_{6.5}

TL;DR

This paper proposes a quasiparticle transition model to explain the one-dimensional incommensurate spin susceptibility observed in underdoped YBa_2Cu_3O_{6.5}, challenging stripe-based interpretations and aligning with experimental anisotropy.

Contribution

It introduces a novel quasiparticle transition model that accounts for anisotropic spin susceptibility in underdoped cuprates, offering an alternative to stripe-based explanations.

Findings

Model reproduces experimental anisotropic spin response.

Transitions between Fermi surface arcs are resonantly enhanced.

Anisotropic gap at saddle points explains observed anisotropy.

Abstract

Recent inelastic neutron scattering measurements found that the spin susceptibility of detwinned and highly ordered ortho-II YBa_2Cu_3O_{6.5} exhibits, in both the normal and superconducting states, one-dimensional incommensurate modulations at low energies which were interpreted as a signature of dynamic stripes. We propose an alternative model based on quasiparticle transitions between the arcs of a truncated Fermi surface. Such transitions are resonantly enhanced by scattering to the triplet spin resonance. We show that the anisotropy in the experimental spin response is consistent with this model if the gap at the saddle points is anisotropic.