Neutron tomography of magnetic Majorana fermions in a proximate quantum spin liquid

TL;DR

This study uses neutron tomography to detect magnetic Majorana fermions in a proximate quantum spin liquid material, revealing stable scattering signals consistent with Majorana excitations and advancing understanding of topological quantum states.

Contribution

It demonstrates the use of four-dimensional neutron tomography to identify and analyze magnetic Majorana fermions in a real material, providing new experimental evidence for topological quantum spin liquids.

Findings

Unprecedented scattering column stable over temperature

Signals consistent with Majorana excitations in Kitaev's model

Insights into perturbations affecting ideal topological states

Abstract

Quantum matter provides an effective vacuum out of which arise emergent particles not corresponding to any experimentally detected elementary particle. Topological quantum materials in particular have become a focus of intense research in part because of the remarkable possibility to realize Majorana fermions, with their potential for new, decoherence-free quantum computing architectures. In this paper we undertake a study on high-quality single crystal of $\alpha-RuCl_3$ which has been identified as a material realizing a proximate Kitaev state, a topological quantum state with magnetic Majorana fermions. Four-dimensional tomographic reconstruction of dynamical correlations measured using neutrons is uniquely powerful for probing such magnetic states. We discover unusual signals, including an unprecedented column of scattering over a large energy interval around the Brillouin zone center which is remarkably stable with temperature. This is straightforwardly accounted for in terms of the Majorana excitations present in Kitaev's topological quantum spin liquid. Other, more delicate, features in the scattering can be transparently associated with perturbations to an ideal model. This opens a window on emergent magnetic Majorana fermions in correlated materials.