Identification of Magnetic Interactions and High-field Quantum Spin Liquid in $α$-RuCl$_3$

Abstract

The frustrated magnet α-RuCl 3 constitutes a fascinating quantum material platform that harbors the intriguing Kitaev physics. However, a consensus on its intricate spin interactions and field-induced quantum phases has not been reached yet. Here we exploit multiple state-of-the-art many-body methods and determine the microscopic spin model that quantitatively explains major observations in α-RuCl 3 , including the zigzag order, double-peak specific heat, magnetic anisotropy, and the characteristic M-star dynamical spin structure, etc. According to our model simulations, the in-plane field drives the system into the polarized phase at about 7 T and a thermal fractionalization occurs at finite temperature, reconciling observations in different experiments. Under out-of-plane fields, the zigzag order is suppressed at 35 T, above which, and below a polarization field of 100 T level, there emerges a field-induced quantum spin liquid. The fractional entropy and algebraic low-temperature specific heat unveil the nature of a gapless spin liquid, which can be explored in high-field measurements on α-RuCl 3 .

A magnetic continuum observed by terahertz spectroscopy in a quantum spin liquid candidate BaCo$_2$(AsO$_4$)$_2$

“…Note that we did not observe the recovery of the continuum with in-plane field, which is consistent with the expectation of an unstable in-plane field induced QSL phase. The recovery of the continuum has not been observed in α-RuCl 3 or other previous Kitaev QSL candidates due to the very large magnetic fields (> 50 T) that are expected to be required to suppress the ordered state [19].…”

“…The in-plane magnetic field required to destabilize magnetic order is as large as 8 T in α-RuCl 3 due to these non-idealities [13][14][15]. An QSL induced by out-of-plane field has not been observed in α-RuCl 3 , and critical fields as large as 50 T have been proposed [19]. Hence, discovering a material that can minimize the non-Kitaev terms is essential.…”