Department of Applied Physics, Stanford University, Stanford, CA, 94305, USA.
Stanford Institute for Materials and Energy Sciences, SLAC & Stanford University, Stanford, CA, 94025, USA.
Nat Commun. 2017 Oct 30;8(1):1192. doi: 10.1038/s41467-017-00876-y.
The search for quantum spin liquids in frustrated quantum magnets recently has enjoyed a surge of interest, with various candidate materials under intense scrutiny. However, an experimental confirmation of a gapped topological spin liquid remains an open question. Here, we show that circularly polarized light can provide a knob to drive frustrated Mott insulators into a chiral spin liquid, realizing an elusive quantum spin liquid with topological order. We find that the dynamics of a driven Kagome Mott insulator is well-captured by an effective Floquet spin model, with heating strongly suppressed, inducing a scalar spin chirality S · (S × S ) term which dynamically breaks time-reversal while preserving SU(2) spin symmetry. We fingerprint the transient phase diagram and find a stable photo-induced chiral spin liquid near the equilibrium state. The results presented suggest employing dynamical symmetry breaking to engineer quantum spin liquids and access elusive phase transitions that are not readily accessible in equilibrium.
最近，人们对在受挫量子磁体中寻找量子自旋液体产生了浓厚的兴趣，各种候选材料都受到了密切关注。然而，一个有能隙的拓扑自旋液体的实验证实仍然是一个悬而未决的问题。在这里，我们表明圆偏振光可以提供一个旋钮，将受挫的莫特绝缘体驱动到手征自旋液体中，从而实现了具有拓扑序的难以捉摸的量子自旋液体。我们发现，驱动的 kagome 莫特绝缘体的动力学很好地被一个有效的弗洛赫特自旋模型所捕捉，其中加热被强烈抑制，诱导出一个标量自旋手性 S·(S × S)项，该项动态地打破时间反演，同时保持 SU(2)自旋对称性。我们标记了瞬态相图，并在平衡态附近找到了一个稳定的光诱导手征自旋液体。所提出的结果表明，利用动力学对称破缺来设计量子自旋液体，并获得在平衡状态下不易获得的难以捉摸的相变。
