Possible Quantum Paraelectric State in Kitaev Spin Liquid Candidate H$_{3}$LiIr$_{2}$O$_{6}$

TL;DR

This study investigates hydrogen ion dynamics in H$_{3}$LiIr$_{2}$O$_{6}$, revealing electric dipole formation and fluctuations that may induce a Kitaev quantum spin liquid state through renormalized magnetic interactions.

Contribution

It introduces a model of proton-induced electric dipoles in H$_{3}$LiIr$_{2}$O$_{6}$ and links dipole fluctuations to the emergence of a Kitaev quantum spin liquid.

Findings

Dipole excitations have an energy gap of about 60 meV.

Protons form electric dipoles with adjacent oxygen ions.

Dipole fluctuations influence magnetic interactions, promoting a QSL state.

Abstract

A new quantum spin liquid (QSL) candidate material H$_{3}$LiIr$_{2}$O$_{6}$ was synthesized recently and was found not to show any magnetic order or phase transition down to low temperatures. In this work, we study the quantum dynamics of the hydrogen ions, i.e., protons, in this material by combining first-principles calculations and theoretical analysis. We show that each proton and its adjacent oxygen ions form an electric dipole. The dipole interactions and the proton tunneling are captured by a transverse-field Ising model with a quantum disordered paraelectric ground state. The dipole excitations have an energy gap $\Delta_{\mathrm{d}}\simeq 60$ meV, and can be probed by the infrared optical spectroscopy and the dielectric response. We argue that the electric dipole fluctuations renormalize the magnetic interactions in H$_{3}$LiIr$_{2}$O$_{6}$ and lead to a Kitaev QSL state.