Emergent orbital magnetization in Kitaev quantum magnets

TL;DR

This paper predicts an emergent orbital magnetization in Kitaev quantum magnets under an external magnetic field, providing a potential experimental signature for identifying the elusive Kitaev quantum spin liquid phase.

Contribution

It introduces the concept of orbital magnetization as a signature of Kitaev QSL and details its microscopic origin and how it can be manipulated and detected experimentally.

Findings

Orbital magnetization can be flipped by rotating the magnetic field.

Derived localized electrical loop current operator in terms of spins.

Estimated loop currents and textures in the Kitaev QSL ground state.

Abstract

Unambiguous identification of the Kitaev quantum spin liquid (QSL) in materials remains a huge challenge despite many encouraging signs from various measurements. To facilitate the experimental detection of the Kitaev QSL, here we propose to use remnant charge response in Mott insulators hosting QSL to identify the key signatures of QSL. We predict an emergent orbital magnetization in a Kitaev system in an external magnetic field. The direction of the orbital magnetization can be flipped by rotating the external magnetic field in the honeycomb plane. The orbital magnetization is demonstrated explicitly through a detailed microscopic analysis of the multiorbital Hubbard-Kanamori Hamiltonian and also supported by a phenomenological picture. We first derive the localized electrical loop current operator in terms of the spin degrees of freedom. Thereafter, utilizing the Majorana representation, we estimate the loop currents in the ground state of the chiral Kitaev QSL state, and obtain the consequent current textures, which are responsible for the emergent orbital magnetization. Finally, we discuss the possible experimental techniques to visualize the orbital magnetization which can be considered as the signatures of the underlying excitations.