标题： 光谱学证据表明二维莫特绝缘体中可能存在量子自旋液体行为 显示英文标题

标题： Spectroscopic evidence for possible quantum spin liquid behavior in a two-dimensional Mott insulator

摘要： 莫特绝缘体具有局域磁矩，当量子涨落足够强以抑制自旋的有序时，将表现出量子自旋液体（QSL）状态。 这种纠缠态将产生集体激发，在这种激发中，自旋和电荷信息是分开传递的。 我们对单层1T-TaS2的角分辨光电子能谱（ARPES）测量显示，在布里渊区中心附近有一个平带，并且在低温下出现约200 meV的能隙，表明该系统具有二维莫特绝缘特性。 这个平带在动量空间中没有色散，但在布里渊区中心附近显示出异常宽的宽度，且光谱权重随着动量的增加而迅速衰减。 这一观察结果被描述为电子分数量化产生的谱连续体，得到了一个低能有效模型的支持。 通过磁性吸附原子进行表面掺杂会降低平带的强度，能隙关闭，这是由于自旋杂质与自旋子和电荷子之间的相互作用导致电荷重新分布的结果。 用非磁性杂质掺杂则表现不同，因为化学势的移动占主导地位。 这些发现为二维三角晶格上强关联电子的QSL状态提供了新的见解。 显示英文摘要

摘要： Mott insulators with localized magnetic moments will exhibit a quantum spin liquid (QSL) state when the quantum fluctuations are strong enough to suppress the ordering of the spins. Such an entangled state will give rise to collective excitations, in which spin and charge information are carried separately. Our angle-resolved photoemission spectroscopy (ARPES) measurements on single-layer 1T-TaS2 show a flat band around the zone center and a gap opening of about 200 meV in the low temperature, indicating 2D Mott insulating nature in the system. This flat band is dispersionless in momentum space but shows anomalously broad width around the zone center and the spectral weight decays rapidly as momentum increases. The observation is described as a spectral continuum from electron fractionalization, corroborated by a low energy effective model.The intensity of the flat band is reduced by surface doping with magnetic adatoms and the gap is closing, a result from the interaction between spin impurities coupled with spinons and the chargons, which gives rise to a charge redistribution. Doping with nonmagnetic impurities behaves differently as the chemical potential shift dominates. These findings provide insight into the QSL states of strongly correlated electrons on 2D triangular lattices.