The localization of charge carriers by electronic repulsion was suggested by Mott in the 1930s to explain the insulating state observed in supposedly metallic NiO. The Mott metal–insulator transition has been subject of intense investigations ever since^1,2,3—not least for its relation to high-temperature superconductivity⁴. A detailed comparison to real materials, however, is lacking because the pristine Mott state is commonly obscured by antiferromagnetism and a complicated band structure. Here we study organic quantum spin liquids, prototype realizations of the single-band Hubbard model in the absence of magnetic order. Mapping the Hubbard bands by optical spectroscopy provides an absolute measure of the interaction strength and bandwidth—the crucial parameters that enter calculations. In this way, we advance beyond conventional temperature–pressure plots and quantitatively compose a generic phase diagram for all genuine Mott insulators based on the absolute strength of the electronic correlations. We also identify metallic quantum fluctuations as a precursor of the Mott insulator–metal transition, previously predicted but never observed. Our results suggest that all relevant phenomena in the phase diagram scale with the Coulomb repulsion U, which provides a direct link to unconventional superconductivity in cuprates and other strongly correlated materials.

莫特（Mott）在1930年代提出了通过电子排斥使载流子局部化的原因，以解释在所谓的金属NiO中观察到的绝缘状态。自^1,2,3以来，Mott金属-绝缘体的转变一直是研究的热点，尤其是它与高温超导性的关系⁴。但是，由于与原始材料的Mott状态通常会被反铁磁性和复杂的能带结构所遮盖，因此缺乏与真实材料的详细比较。在这里，我们研究有机量子自旋液体，在没有磁序的情况下单带Hubbard模型的原型实现。通过光谱法绘制哈伯带的映射图，可以绝对地测量相互作用强度和带宽，而相互作用强度和带宽是进入计算的关键参数。通过这种方式，我们超越了常规的温度-压力曲线图，并基于电子相关性的绝对强度为所有真正的Mott绝缘子定量组成了通用相图。我们还将金属量子涨落确定为莫特绝缘子-金属跃迁的先兆，先前曾预测过但从未观察到。U，它直接连接到铜酸盐和其他高度相关的材料中的非常规超导性。