Neutron scattering signatures of the 3D hyper-honeycomb Kitaev quantum spin-liquid

TL;DR

This paper analyzes the dynamical structure factor of a 3D Kitaev quantum spin-liquid, revealing features like a response gap and Majorana fermion signatures, and highlights inelastic neutron scattering as an effective probe.

Contribution

It provides the first detailed study of the dynamical structure factor in a 3D hyper-honeycomb Kitaev QSL, showing qualitative similarities with 2D models despite dimensional differences.

Findings

Presence of a response gap in the 3D QSL

Energy dependence linked to Majorana fermion density of states

Inelastic neutron scattering as a key experimental probe

Abstract

Motivated by recent synthesis of the hyper-honeycomb material $\beta$-$\mathrm{Li_2 Ir O_3}$, we study the dynamical structure factor (DSF) of the corresponding 3D Kitaev quantum spin-liquid (QSL), whose fractionalised degrees of freedom are Majorana fermions and emergent flux-loops. Properties of this 3D model are known to differ in important ways from those of its 2D counterpart -- it has finite-temperature phase transition, as well as distinct features in Raman response. We show, however, that the qualitative behaviour of the DSF is broadly dimension-independent. Characteristics of the 3D DSF include a response gap even in the gapless QSL phase and an energy dependence deriving from the Majorana fermion density of states. Since the majority of the response is from states containing a single Majorana excitation, our results suggest inelastic neutron scattering as the spectroscopy of choice to illuminate the physics of Majorana fermions in Kitaev QSLs.