Abstract
The frustrated magnet α-RuCl3 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-RuCl3, 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-RuCl3.
Highlights
The frustrated magnet α-RuCl3 constitutes a fascinating quantum material platform that harbors the intriguing Kitaev physics
We study the K-J-Γ-Γ0 honeycomb model with the interactions constrained within the nearest-neighbor sites, i.e., H1⁄4
While the zigzag order can be induced by the third-neighbor Heisenberg coupling J332,33,51, we constrain ourselves within a minimal K-J-Γ-Γ0 model in the present study and leave the discussion on the J3 coupling in the Supplementary Note 1
Summary
The frustrated magnet α-RuCl3 constitutes a fascinating quantum material platform that harbors the intriguing Kitaev physics. 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. Due to additional non-Kitaev interactions in the material, α-RuCl3 exhibits a zigzag antiferromagnetic (AF) order at sufficiently low temperature (Tc ≃ 7 K)[2,14,15], which can be suppressed by an external in-plane field of 7-8 T16–18. Measurements suggest the presence of fractional excitations and the proximity of α-RuCl3 to a quantum spin liquid (QSL) phase[14,15,19]. The unusual (even half-integer quantized) thermal Hall signal was observed in a certain temperature and field window[28,29,30,31], suggesting the emergent Majorana fractional excitations. Through large-scale calculations, we determine an effective Kitaev-Heisenberg-Gamma-Gamma[0] (K-J-Γ-Γ0) model [cf. Eq (1)
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