Recent theoretical investigations of quantum spin liquids have described phenomenology amenable to experimental observation using scanning tunneling microscopy. This includes characteristic resonances found at the edge of the upper Hubbard band of the host Mott insulator, that under certain conditions shift into the Mott gap under external magnetic field [W.-Y. He and P. A. Lee, arXiv:2212.08767]. In light of this we report scanning tunneling microscopy observations, in samples of the quantum spin liquid candidate $1T\text{−}{\mathrm{TaS}}_2$, of a conductance peak at the upper Hubbard band edge and its magnetic field dependent behavior. These observations potentially represent evidence for the existence of a quantum spin liquid in $1T\text{−}{\mathrm{TaS}}_2$. We also observe samples in which such field dependence is absent, but with no observed correlate for the presence or absence of field dependence. This suggests one or more material properties controlling electronic behavior that are yet to be understood, and should help to motivate renewed investigation of the microscopic degrees of freedom in play in $1T\text{−}{\mathrm{TaS}}_2$, as well as the possible realization of a quantum spin liquid phase.

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• Quantum spin liquid
• Layered crystals
• Mott insulators
• Transition metal dichalcogenides
• Scanning tunneling microscopy
• Scanning tunneling spectroscopy