studied by neutron scattering

BaCo₂V₂O₈ is a realization of a spin-1/2 Ising-like quasi-one dimensional antiferromagnet (AF) with fascinating static and dynamical behaviors. In zero-field, the weak interchain interactions stabilize below 5.6 K a peculiar Néel ordering, characterized by magnetic moments aligned along the chain c-axis and dressed with confined two spinon excitations [1,2]. We have explored the influence of an external magnetic field both on the AF ordering and on the spin dynamics by single-crystal neutron scattering. Different behaviors are observed for a transverse and a longitudinal magnetic field (i.e. perpendicular and parallel to the direction of the moments, respectively), nicely reproduced by TEBD numerical calculations.
In a transverse magnetic field H // b, a staggered field is induced along the a direction, due to the non-diagonal anisotropic g-tensor of BaCo₂V₂O₈. As a result, a high field novel phase settles above a critical field of 10 T, when the staggered field overcomes both the Ising anisotropy and the interchain coupling. The nature of the excitations is also strongly modified. As I will show, our results reveal the occurrence of a topological quantum phase transition between two types of solitonic topological objects [3].
In a longitudinal magnetic field H // c, the Néel ordering turns at a critical field of 3.8 T into a longitudinal incommensurate (IC) one, with magnetic IC excitations, due to the Ising character of the system [1]. This phase has raised a strong interest as it is a unique example of the Tomonaga-Luttinger liquid (TLL) physics experimentally accessible under moderate magnetic field. I will present our results on the dispersion spectrum in this exotic phase together with its magnetic field dependence, in the light of the TLL theory [4].
[1] E. Canévet et al., PRB 87, 054408 (2013).
[2] B. Grenier et al., PRL 114, 017201 (2015) & PRL 115, 119902 (2015).
[3] Q. Faure et al., Nat. Phys. 14, 867 (2018).
[4] Q. Faure et al., PRL 123, 027204 (2019).