2025/09/08 by Li, Yi, Shangguan, Yanyan, Wang, Xinzhe +10
#FOS: Physical sciences #Strongly Correlated Electrons (cond-mat.str-el)
paper · doi:10.48550/arxiv.2509.06753
The honeycomb magnet α-RuCl3 has been a leading candidate for realizing the Kitaev quantum spin liquid (QSL), but its intrinsic spin dynamics have remained obscured by crystal twinning. Here we apply biaxial anisotropic strain to detwin α-RuCl3 single crystals and directly visualize the intrinsic magnetic excitations using inelastic neutron scattering. We discover that the low-energy spin waves emerge from the M points -- transverse to the magnetic Bragg peaks -- providing direct evidence of anisotropic magnetic interactions in α-RuCl3. The intrinsic spin-wave spectrum imposes stringent constraints on the extended Kitaev Hamiltonian, yielding a refined, quantitatively consistent set of exchange couplings for the zigzag ground state and its low-energy dynamics. Above the magnon band, we uncover broad excitation continua: while a twofold-symmetric feature near 6 meV at Γ is consistent with bimagnon scattering, the dominant spectral weight forms a sixfold-symmetric continuum extending up to ∼ 16 meV that cannot be explained by conventional magnons. This strongly supports the presence of fractionalized excitations-a hallmark of Kitaev QSL physics. Our findings establish biaxial strain as a powerful symmetry-breaking probe to access the intrinsic spin dynamics of Kitaev materials and provide critical benchmarks for refining theoretical models of quantum magnetism in α-RuCl3.