New phases with broken discrete Ising symmetries are uncovered in quantum materials with strong electronic correlations. The two-leg ladder cuprate Sr_14−xCa_xCu₂₄O₄₁ hosts a very rich phase diagram where, upon hole doping, the system exhibits a spin liquid state ending to an intriguing ordered magnetic state at larger Ca content. Using polarized neutron diffraction, we report here the existence of short range magnetism in this material for two Ca contents, whose origin cannot be ascribed to Cu spins. This magnetism develops exclusively within the two-leg ladders with a diffraction pattern at forbidden Bragg scattering, which is the hallmark of loop current-like magnetism breaking both time-reversal and parity symmetries. Our discovery shows local discrete symmetry breaking in a one dimensional spin liquid system as theoretically predicted. It further suggests that a loop current-like phase could trigger the long range magnetic order reported at larger doping in two-leg ladder cuprates.

具有强电子相关性的量子材料中发现了具有破碎的离散伊辛对称性的新相。两腿梯形铜酸盐S r _{14− x} C a _x C u ₂₄ O ₄₁拥有一个非常丰富的相图，其中在掺杂空穴后，系统表现出自旋液体状态，并在较大的C a含量时终止于吸引人的有序磁性状态。使用极化中子衍射，我们在此报告了这种材料中存在两个C a的短程磁性含量不能归因于铜自旋。这种磁性仅在两腿阶梯内产生，并具有在布拉格布拉格散射处的衍射图样，这是环状电流状磁性的标志，打破了时间反转和奇偶对称。我们的发现显示了一维自旋液体系统中的局部离散对称性破裂，如理论上预测的那样。这进一步表明，类似环形电流的相位可能会触发在两脚梯形铜酸盐中较大掺杂时报告的远距离磁阶。