Quantum spin liquids (QSLs) are in a quantum disordered state that is highly entangled and has fractional excitations. As a highly sought-after state of matter, QSLs were predicted to host spinon excitations and to arise in frustrated spin systems with large quantum fluctuations. Here we report on the experimental observation and theoretical modeling of QSL signatures in monolayer 1T-NbSe₂, which is a newly emerging two-dimensional material that exhibits both charge-density-wave (CDW) and correlated insulating behaviors. By using scanning tunneling microscopy and spectroscopy (STM/STS), we confirm the presence of spin fluctuations in monolayer 1T-NbSe₂ by observing the Kondo resonance as monolayer 1T-NbSe₂ interacts with metallic monolayer 1H-NbSe₂. Subsequent STM/STS imaging of monolayer 1T-NbSe₂ at the Hubbard band energy further reveals a long-wavelength charge modulation, in agreement with the spinon modulation expected for QSLs. By depositing manganese-phthalocyanine (MnPc) molecules with spin S = 3/2 onto monolayer 1T-NbSe₂, new STS resonance peaks emerge at the Hubbard band edges of monolayer 1T-NbSe₂. This observation is consistent with the spinon Kondo effect induced by a S = 3/2 magnetic impurity embedded in a QSL. Taken together, these experimental observations indicate that monolayer 1T-NbSe₂ is a new promising QSL material.

量子自旋液体（QSL）处于高度纠缠且具有分数激发的量子无序状态。作为一种备受追捧的物质态，QSL 预计会产生自旋子激发，并出现在具有大量子涨落的受挫自旋系统中。在这里，我们报告了单层 1T-NbSe ₂中 QSL 特征的实验观察和理论建模，这是一种新兴的二维材料，表现出电荷密度波 (CDW) 和相关的绝缘行为。通过使用扫描隧道显微镜和光谱学（STM/STS），我们通过观察单层 1T-NbSe ₂与金属单层 1H-NbSe ₂相互作用时的近藤共振来确认单层 1T-NbSe ₂中存在自旋涨落。随后在哈伯德带能量下对单层 1T-NbSe ₂进行 STM/STS 成像，进一步揭示了长波长电荷调制，与 QSL 预期的自旋调制一致。通过将自旋S = 3/2 的锰酞菁 (MnPc) 分子沉积到单层 1T-NbSe ₂上，新的 STS 共振峰出现在单层 1T-NbSe ₂的哈伯德带边缘。这一观察结果与嵌入 QSL 中的S = 3/2 磁性杂质引起的自旋近藤效应一致。总而言之，这些实验观察结果表明单层 1​​T-NbSe ₂是一种新的有前途的 QSL 材料。