2D proximate quantum spin liquid state in atomic-thin α-RuCl₃

Two-dimensional (2D) atomic crystals have made major inroads into condensed-matter physics and give rise to fascinating phenomena due to quantum confinement. Here we report the first Raman scattering study on phonon-magnetic scattering coupling, proximate quantum spin liquid ground state and collective fractionalized excitations in exfoliated α-RuCl₃ atomic layers. Our results uncover that 2D α-RuCl₃ could harbour the unusual magnetic continuum, serving as a hallmark of the 2D proximate quantum spin liquid state and frustrated magnetic interactions. More importantly, our work demonstrates that the unusual magnetic scattering, as compared with bulk, is more obvious in 2D α-RuCl₃, indicating that the frustrated magnetic interactions are enhanced strongly. Such unusual enhancement of frustrated magnetic interactions may be responsible for the gigantic phonon-magnetic scattering coupling of 2D α-RuCl₃ and play a key role in stabilizing the 2D proximate quantum spin liquid state. Our work establishes a firm basis for exploring and understanding the 2D proximate quantum spin liquid and fractionalized excitations based on the atomically thin α-RuCl₃.